Vector

Synopsis
A deadly virus is spreading through LA and only Charlie's equations can determine how far and where the disease is headed. The CDC is also on the case, and Don has to contend with a potential turf war among the authorities.

Plot
A mother and her three sons are in the car on the way to school in the morning. The eldest son says he's feeling sick. A husband asks his wife if she knows where a specific tie is before work as she is sick in the bathroom. Two young women are talking about work.

The mother realises that the eldest boy has a fever. The husband hears a crash in the bathroom. One of the young women coughs at the bus stop.

The mother takes her son to the doctor. He passes out on the way there. The husband finds his wife passed out in he bathroom. The coughing woman doesn't wake up when the bus comes.

Don and Terry show up to a CDC scene and Lt. Havercamp, the Public Health Service lead, introduces herself. The son from earlier is one of six that have died from an unknown illness. The neighbourhood is under quarantine. They need a math expert to help in the case. Lt. Havercamp says that they'll be using their expert as they have the necessary clearance as it will take at least a month to get any FBI expert the necessary clearance for a possible bio-terrorism case. A car rolls up and out comes Charlie. Don is surprised by Charlie's Top Clearance status. The mother from the opening scene is rolled out in a quarantined stretcher as she is sick as well.

Don and Lt. Havercamp brief the team at large. Charlie explains how infection is spread and how quickly. He needs more data to find patient zero. The team interviews victims, friends, and family. Alan sees Charlie working on the case and probes him about it. At the FBI Charlie used the data found to begin to map out where the infection could have started from. He uses a growing plant as an analogy to explain how what he's doing works. He gets more data and they find that Union Station has a high probability of being the starting point. Charlie is uncertain of his findings. Lt. Havercamp informs Charlie who then informs the core team that the infection is the Pandemic (Spanish) Flu.

Alan is about to leave for Downtown LA, but the brothers try to convince him to stay home.

Four labs study the Spanish Flu. One is in LA. Don goes to talk to Weaver, a scientist that works there about the outbreak. Only three scientists have access to the flu virus. They talk to the other two scientists.

Charlie still isn't 100% sure about his solution. He goes to Larry for help. He comes up with another possible outbreak point. After plugging in his new data more of the cases of the sick people are accounted for. This leads them to believe that the sickness is linked to the buses rather than the trains at Union Station. Also, people in one direction are getting sicker than those in the opposite direction. It turns out there are two different strains of Spanish Flu have been released, the second originating from a lab out of Maryland.

Alan comes home from being Downtown. Charlie is worried about him.

Working with Charlie, Lt. Havercamp finds that they may be able to treat those afflicted with the virus with the treatment for a different pathogen. Charlie thanks Larry for his help.

Walsh, one of the scientists, is brought in for questioning. He used to work for the lab in Maryland. He brought a sample of the other lab's strain across the country to help them try to win a contract with a pharmaceutical company.

Don learns that Charlie did work for the NSA and that's how he got his clearance.

The team gets the tapes from the bus depot and see that Weaver was present at the depot around the time that the illness was released. He is arrested outside of a church with candles to light for the victims.

The Eppes family converges on the porch and Don tries to get Charlie to spill the beans on his past NSA assignment.

Main

 * Rob Morrow as Don Eppes
 * David Krumholtz as Charlie Eppes
 * Judd Hirsch as Alan Eppes
 * Alimi Ballard as David Sinclair
 * Sabrina Lloyd as Terry Lake
 * Peter MacNicol as Larry Fleinhardt

Guest

 * CCH Pounder as Lt. Havercamp
 * Rainn Wilson as Martin Grolsch
 * Elizabeth Connors as Claudia Kramer
 * Marita Geraghty as Jessica Avery
 * Anjul Nigam as Dr. Renfro
 * J.K. Simmons as Dr. Clarence Weaver
 * Dean Shelton as Joshua Kramer
 * Tanner Richie as David Kramer
 * Cody Estes as Ryan Kramer

Title
In everyday usage, the term "angle" is often substituted, however, technically, a vector is "a quantity possessing both magnitude and direction". Such distinctions lead us into Charlie's territory.

Trivia
Rainn Wilson's character (Martin Grolsch) is named after one of the most popular Dutch beers: Grolsch. Grolsch is named after a town, and it's not at all a common last name, not even in The Netherlands.

Goofs
When the public health officer, Lt. Havercamp, is first introduced she is introduced as "Commander." As shown by the credits and her shoulder boards (two full-size stripes), she is a lieutenant. PHS ranks are the same as navy officer ranks.

Crazy Credits
[This appears on the beginning of the episode] 4 Counties, 6 Deaths, 30 Cases, 1 Unknown Pathogen