Cause and Effect

Charlie and Amita are getting married at last. While making an arrest, Don's gun is stolen from him and is subsequently used in a series of crimes. Agent Ian Edgerton appears briefly in the series finale, along with other popular recurring characters such as Dr. Otto Bahnhoff and Matt Li to round things off.

Title
One of the most fundamental precepts of physics - a chain of causality. A number of key storylines are thus resolved, major plot elements laid peacefully to rest.

Trivia

 * Don has been an FBI agent for 15 years, and worked with David for 6 years.
 * Charlie's middle name is Edward.
 * This is the second time Don got his gun stolen, the first time is in the second episode of the first season.
 * Last episode of the show.

Goofs
Although Mazzolla's driver license address says the house number is 344, when the FBI agents leave the house the number on the pillar is 525.

Mazzolla and Hiller are next door neighbors in a cul-de-sac, yet their driver licenses show completely different addresses in different ZIP Codes.

Crazy Credits
[This appears on the beginning of the episode] 850 grams-weight 153 millimeters-line of sight 2.5 kilograms-trigger pull Glock model 19