|“||Some people drink, some gamble, I analyze data.||”|
–Charlie Eppes, Disturbed
As a child prodigy, Charlie's childhood was unique and most certainly not easy. He could multiply four-digit numbers in his head when he was three years old and was working with special teachers at four years old. He attended high school at the same time as his older brother, moving on to Princeton University at age thirteen, graduating when he was sixteen.
His paper on the Eppes Convergence cemented his place in the mathematical world. While attending Princeton University, he met Larry Fleinhardt, his teacher and mentor, who would eventually become a close friend.
After graduating from university, Charlie went back home and took a job at the California Institute of Science. He lived in his parent's home but had very little contact with his brother, who was in New Mexico working in Fugitive Recovery at the time.
About one year before The Pilot, Charlie's mother, Margaret, fell ill with cancer, and Don left New Mexico to stay with the family. During this time, Charlie receded into his work, in denial about his mother's state, causing a lot of tension between Don and Charlie as their mother continued to weaken.
When their mother passed away, Charlie and Don drifted apart, though Don stayed in California and took a job at the FBI.
Charlie is stubborn and hardworking to the point of being obsessive. Alan once states that although Charlie is very observant in certain areas, he sometimes completely misses other things. Charlie is easily captivated by a problem presented to him and will work tirelessly to solve it, often staying up long hours in his garage with his chalkboards full of equations. He is often very enthusiastic about his work and eager to share excessive explanations with anyone who will pause to listen. He talks fast and is a little disorganized; never standing still, gesturing with his hands and stacking papers everywhere.
Charlie also has a very strong sense of right versus wrong and feeling of guilt. When taking a polygraph test, he is extremely nervous and anxious, confessing to childhood crimes such as stealing a baseball card from a friend and accidentally killing his brother's class gerbil. Charlie is quite idealistic when it comes to social problems and relationships as evidenced clearly throughout the series, especially in season 5, when he questions his work with the FBI.
Charlie can be incredibly stubborn and child-like when upset and holds strong grudges against people who he feels have wronged him. Charlie is described by Larry as egotistical, but he is extremely loyal to his family and friends, doing anything in his power to keep them healthy, safe, and happy.
Charlie is occasionally a little naive when it comes to human behavior, being a child prodigy in the math world. However, this is not one of Charlie's prominent characteristics, as he is quite capable of handling himself properly in social situations.
Charlie is a rationalist. He is disbelieving of UFOs and psychics and disapproves of magic and gambling. He is not willing to suspend his disbelief or take chances as his thought process is very mathematically based. However, Charlie is fairly open to religion and faith - his family is of Jewish descent but doesn't really practice the religion, but Charlie is supporting of his brother when Don decides to find himself through Judaism.
The episode "Uncertainty Principle" is significant for the backstory it gives on the familial relationships, particularly Charlie's difficulty in dealing with their mother's death from cancer. While it's unclear how Don reacted, Charlie spent the last three months of his mother's life isolated in the garage, incessantly working on one of the Millennium Prize Problems, specifically P vs NP; it's a point of contention between the brothers. Also, Charlie doesn't think Don understood what he went through during their school years, especially how he was treated as "Don's brainiac little brother" by his peers in high school, and how he often left him to his own resources as a child, though he was not as inept as Don had presumed. However, Charlie's relationship with Don remains strong, as he has begun to increasingly fear for his brother's safety on the job and still looks to his older brother for acceptance. Charlie and his father worry about Don committing to relationships, and for a time, fear that he had been cheating on Robin Brooks. Ironically, Charlie has similar problems with women himself. After a couple dozen murder cases, Charlie is somewhat jaded and world-weary like his brother. FBI agent David Sinclair of Don's team even comments that he has never seen two brothers so similar and yet so different. In "The Janus List", the brothers seem to take on each other's tendencies a bit. Though, in season five, Charlie is dismayed that Don does not reveal to him his newfound religious faith.
In "Prime Suspect," Charlie purchases the beautiful craftsman family home from his father, who continues to live with him. Now 30 years old, Charlie wants to be responsible and take care of his father, but still believes that much of the pressures involving their dad has been put on his shoulders, as Don doesn't seem to have enough time. Realizing this, Alan sets his sights on moving out to accomplish things on his own, with Charlie seemingly supporting the idea, but has since chosen to stay as he favors his son's company. Recently, Charlie is bothered by his father trying to impose his will on him with maintaining the house, as he is a full tenured professor at one of the most prestigious institutions in the country working on "life-altering" mathematics, i.e., in solving crimes. Alan just wants him to be responsible and not end up like Larry, though Mr. Eppes respects Fleinhardt. Even he has thought of this possibility and decides to do more around the home. After Charlie compares his own situation to that of Einstein his father looks into information on the physicist and understands his son's predicament. Charlie also feels guilty about the amount of time his parents, particularly his mother, who always was attuned to his way of thinking, spent with him as a child; he even asks his mother in a dream if she regrets the time away from Don and Alan because of the special attention he needed growing up.
Charlie's research often interferes with his relationships: as with Amita on their first date, for all they could talk about is mathematics; Fleinhardt says that it is a common interest and they should not struggle to avoid the subject. Charlie and Amita had several false starts. Charlie has also spent some time with his ex-girlfriend, Susan Berry, an attractive neuroscientist from London. He had lived with Susan for two years, and Larry described this as his very own Berry's phase. However, she later reveals that she is currently involved with someone else and has to return to England. Charlie attempts to start a relationship with Amita once more, though her job offer at Harvard University strains this possibility and makes him distraught for some time. Eventually, she decides to take the alternative offer at CalSci with the hope to begin a romantic relationship with him, though his fear of possible failure causes him to question whether he wants this second chance; Don cautions him about such an attitude. Amita notices his ambivalence and isn't certain if she wants to back out of the relationship, but he then pushes it forward. Pressures from their colleagues over the inappropriateness of the relationship nearly cost them, but by the middle of the third season their romantic involvement stabilizes and they have grown considerably closer. He feels rejected when Amita does not want him to meet her father, due to his expectations about the men she dates. Initially, he wonders if it is based on him being Jewish, but the problem is that he is not Indian-born. Alan explains that Mr. Ramanujan would like him after meeting him. Charlie and Amita state that they love each other, and have even decided to move in together, though, the actual living arrangement has not been determined. When Amita's parents finally meet him, they are rude, but warm to him later. Alan says that Charlie will have to marry her.
Unforeseen complications with his work emerge as the new Chair of the CalSci Physics, Mathematics, and Astronomy Division, Dr. Mildred Finch, in "Waste Not", makes Charlie head of the Ph.D. admissions committee against his wishes, bogging him down with more work, and gives him pressures about using the school's supercomputer for FBI work or missing classes for such. This leads to Charlie being confrontational, but she calms him when she says she just wants him to be "the Sean Connery of the mathematics department." In "Take Out", Charlie and Millie attend a black tie reception for CalSci fundraising and bond. Soon after, Charlie is asked by Millie to meet with Macmillan Pharmaceuticals, which according to Amita has a reputation for exploiting third-world countries. Amita serves as his conscience in this matter, and he goes to see Dr. Finch about it. With "Pythagorean wit," he dazzles Macmillan and is to serve as a mathematical consultant for the pharmaco-kinetic modelling project, only under the provision that CalSci will administer the trials and monitor the drug at every step, all computational analyses are conducted by Charlie and his team, and 5% of the gross will go to third-world AIDS organizations chosen by Professors Eppes and Ramanujan . In "Democracy", as part of his duties, he recruits the young fantasy baseball and sabermetrics fanatic Oswald Kittner (Jay Baruchel), who shows great promise, to attend CalSci.
When Larry announces his leave of absence to board the International Space Station (in "Brutus"), Charlie is shocked and upset. He is in denial about Larry's ambitions and he thinks the reason for the risks involved will assert itself firmly in Larry's mind. He reasons that apparently, Larry wouldn't do such a thing. Larry remands his few prized possessions to him, and he is grateful for the gesture. When he tells him his concerns, Larry is angered. Amita says to Larry, "[Charlie] has never dreamt of something he couldn't reach, so he has no idea what it is like to want something he is not able to get. So how could he understand how much [Larry] you would give up when this chance comes along?" Larry understands and decides to ignore Charlie's protestations. Though neither apologizes, they are on good terms. Charlie says to Amita that he does not know what he would do without him, as he peruses through Larry's precious items that were bestowed upon him. In "Killer Chat", he says that he was glad that Larry's dream could come true, but feels conflicted about being relieved when he discovers that Larry might have been scrapped from the mission when NASA learned of his eccentric indulgences such as sleeping in the campus steam tunnels. However, Charlie agrees with Megan in wanting to help Larry and personally vouches for him. Eppes' words and affiliation with the NSA gets him back on the mission, thus, repaying a debt as Larry helped launch him into the academic firmament. Earlier, he had given him back his lucky t-shirt.
In "The Art of Reckoning", Charlie is initially overjoyed to see his friend Larry return, but Charlie is dismayed with Larry's lack of enthusiasm for life, so Charlie doesn't object to him readjusting at a monastery. His concern is apparent, and he says he just wants his friend back.
Since then, in "Trust Metric", Charlie is pleased to see his friend doing well, feeling that he needed a friend, and is glad to have focused on teaching while Don did not include him with FBI work; though, on previous occasions, he expressed the desire to be involved. Granger's escape from the prison bus causes him to become active in helping his brother once more, allowing him a chance to use set covering deployment.
Dr. Finch tells him to publish, and so he has renewed interest in old research, having decided to publish one of his eleventh-grade papers he started at nine years old, "The Mathematics of Friendship," with an addendum. A publishing company has turned his work into a classic book for those not mathematically inclined, while opting for a title with more pizazz, "Friendship, As Easy as Pi." Charlie takes joy in the belief that this book will allow his thoughts to reach a much wider audience than before. By "In Security," the published book appears with the title "The Attraction Equation" and a dapper photo on the back cover of him holding a sculpture of a stellated icosidodecahedron with beveled edges. A decision-theoretic approach to relationships is covered in the book. His proud father hands copies to friends and Larry sells signed copies on eBay. He apparently has some fans and gives into a televised interview.
In "Checkmate", Charlie is training in weapons and tactics in LA's FBI school, where he is shown to have a high skill in marksmanship at the range, impressing many of his FBI training peers as well as his instructor, which he credits to following Wyatt Earp's preference for careful accuracy instead of rapid firing. He is given a certificate of marksmanship by the FBI. In "Pay to Play", Charlie convinces Don to let him join the team when they go to arrest a suspect, mentioning that he passed the FBI course.
In the season four finale "When Worlds Collide", Charlie helps an innocent colleague accused of terrorism by sending genetic research to scientists at Pakistani universities which is prohibited, with full cognizance of the consequences. As a result, Charlie is arrested, loses his security clearance and ultimately loses his ability to help Don on FBI cases. Once again, Charlie holds strong to his ideals. In the previous season's "Burn Rate", Charlie has strong opinions concerning genetic engineering, believing bomb suspect, fellow prodigy, and former Feynman student Emmett Glaser's ideas about genetic predeterminism are rational, not incendiary, and helps to clear his name.
The charges against Dr. Eppes are dropped. For a time, Don Eppes' team is attempting to make do with Fleinhardt's and Amita's expertise, but Charles' assistance is sorely missed to the point of consulting him secretly. For his part, Charles has been convinced by his lawyer and father to attempt to have his clearance restored. Even Don supports the idea and stands up to security clearance investigator Carl McGowa, stating to go after him, not his brother. Temporarily, Charlie works as an LAPD consultant until the fiasco with his security clearance can be resolved. He later gets his clearance back and is working with his brother and the FBI again. He is trying to assert himself in the methodology used to solve a crime, having struggled with not being included, but some friction arises with Amita and Larry.
Charlie works once again with rival Marshall Penfield, as they settle their differences ("Frienemies"). Also, he is chosen to be the head of the think tank model comprising himself, Larry, Alan, and Amita ("Jacked"). As Dr. Eppes applies the Turing Test to a seemingly unique artificial intelligence, he is tricked only to come to the realization that the computer only uses a recursive algorithm to apply the most human responses, while simultaneously being tempted by an offer to work for DARPA. Head of DARPA special projects Jane Karellen (Nancy Travis) knows that he has a limited window to use his genius and tells Charlie that he is one of the top five minds on the planet. Amita's life is even threatened by the advanced computer ("First Law").
Late in season five, Charlie moves into a new office. While moving, he gets some inspiration for his cognitive emergence theory, which causes him to momentarily set aside his work on a series of home invasions for Don. Don is stabbed while attempting to arrest the home invaders ("The Fifth Man"). Charlie blames himself for Don being stabbed and throws himself into his FBI consultation work as a result ("Disturbed"). This worries everyone, especially Don, who tells him to "do whatever you want to do" ("Greatest Hits") while visiting Charlie in his new office. Around this time, Charlie is also presented with a series of letters from previous successive holders of this prestigious office, wherein each celebrated mathematician writes of accomplishments they intend to achieve, passing down the torch to the next in line to do the same. At first, Charlie is hesitant, until the very determined Amita convinces him to write the corresponding letter and eases his burdens, as Charlie fears he cannot meet his destiny with so much weight to succeed being placed on his shoulders his entire life. At the end of the season, while leaving for dinner, Charlie is attacked, and Amita is kidnapped. Charlie is so emotionally distraught that he cannot think of the math needed to find Amita. With the help of Don, Alan, and David, Charlie snaps out of it to locate Amita. Amita is rescued. He realizes that he did not want to lose Amita, and he proposes to her ("Angels and Devils").
At the end the premiere episode of the program's sixth season, it was revealed that Amita has accepted Charlie's proposal. The issue was skirted throughout the episode, as the two were waiting until Amita officially received permission from her parents. He and Amita discuss the number of children that they want to have, and they both decide that they may need to participate in the Big Brother/Big Sister program for some practical experience before having children. He and Amita attempt to find a wedding date that is suited to their and their families' schedules; Alan suggests that they should take his and Margaret's anniversary date as Charlie and Amita's date. Charlie and Amita have since pushed the date forward as his academic fantasy has come to light, is a visiting professor at Cambridge University. In the season finale, after the wedding ceremony presided over by Larry, he is happy but worries about disconnecting with Don and offers to have the garage renovated into a guest house for his father. He toasts his friends and family and amazes at the prospect of staying in England with his wife.
Don and Charlie were not very close during childhood, due to the age gap and Don's feelings of inferiority and resentment towards Charlie's math genius. Don disliked Charlie's presence in his school life as his genius younger brother and resented having to tote his younger brother around with him. However, as annoyed and embarrassed as Don was at Charlie being in the same grade as him, Don still protected Charlie from school bullies. When their mother died, Don was angry with Charlie for hiding in the garage during the last months of her life, and they saw very little of each other. However, Charlie's work with Don brought them close together, and over the series, they learned to reconcile their differences and developed a much more friendly, affectionate relationship. They become very close and loyal towards one another; in season 5, Don vouches for Charlie's FBI clearance, risking his own job doing so.
Charlie was especially close with his mother and took her sickness and following passing particularly hard. He spent the last three months of her life in the garage, unable to face her, working on a supposedly impossible question - P vs NP - misguidedly thinking that he may be able to cure her sickness. Because Margaret had supported Charlie all his life, even moving to another state for Charlie's university education, she probably understood Charlie better than the rest of the family.
Charlie was not as close to his father as his mother during his childhood, because Charlie felt that a father should be able to teach their son things, Charlie always tried to keep his math world away from his father. However, as he became an adult, he became closer to his father, and started to learn that Alan had other skills and knowledge to give Charlie. He bought the family home from Alan in season 1 and Alan lives with Charlie for the rest of the series, though talk is made of Alan's moving out, he never does. Alan provides simple, straightforward insight into Charlie's FBI work, his moral conflicts, and his relationship with Don and Amita.
As Charlie's mentor turned friend, Larry has almost a father/son dynamic with Charlie. He looks out for Charlie, helping him with his math problems and providing insight and different perspective for him when he needs it. Larry's thoughts and input if often just what Charlie needs to crack a case in time. In turn, Charlie looks out for Larry, offering him housing when he finds out Larry is living in his office, helping him start his relationship with Megan, and vouching for Larry in order to get Larry into space, and worrying when Larry is disconnected when he comes back from his space mission.
At the beginning of the series, Charlie is Amita's thesis advisor. Charlie initially insists that he does not have feelings for Amita, but soon comes to realize them as the season progresses. After Amita completes her thesis, she becomes a close friend, colleague, and eventually, after a few false starts, his girlfriend. Charlie proposes to her in the Season 5 finale, and they get married in the Season 6 and series finale before they move to Oxford for a year. Amita provides a bit of calm and security in Charlie's life, helping him with his calculations and guiding him through conflicts with his family. She is often the stable, sensible center when it seems Larry and Charlie may well whirl off into imaginary and impractical other realms as they strive to look at a problem from unanticipated angles.
David joined Don's team in the same case that Charlie first got really involved with Don's work, so he really believes and puts faith into Charlie's math. Charlie and David are seen to be close friends. They have had a handful of small disagreements (for example, in 36 Hours) but David is generally fully supportive of Charlie.
When Colby first joined the team, he was disbelieving of Charlie's applications. However, the more he worked on the team, the less dubious he got, and he quickly began to trust the math, and even started to take some sort of pride in Charlie's work and its accuracy. Colby never really understands what Charlie's work really means, and doesn't try as hard as Megan or Liz or David to understand. As Charlie and Colby's work and skills are so different, Colby often ribs Charlie about his 'magical' equations in an almost brotherly way. Charlie seems to trust Colby, going to him for advice (Park Shooting). Even when the team thought Colby was a double-agent, Charlie was the one who encouraged the team to go after Colby and save Colby's life.
Megan is fairly close with Charlie and his family, especially once she and Larry become involved. She is fond of Charlie, affectionately regarding him as almost a little brother. She is very supportive and enthusiastic about Charlie's mathematical work for the FBI, almost right from the beginning. She listens, understands, and remembers a lot of what Charlie explains.
Liz is similar to Megan in terms of level of understanding of Charlie's work. She, along with Megan, remember the most about Charlie's work, surprising the other agents. Charlie and Liz have few scenes alone together, although they seem to get along well.
Like Colby, Nikki was very skeptical of the idea of using math to solve cases, but eventually accepts Charlie's word as truth. She is rarely seen alone with Charlie, but they have never had a major falling out, probably because of their lack of interactions.
- Charlie is one of only two characters (along with Don) to appear in every episode.