When Don and his team are called to the scene of the murder of a Los Angeles gang member, they learn they are investigating the murder of another agent who had been working undercover.

When an ATF agent is found dead under unusual circumstances, Don wants to take the case, which revolves around an elaborate bank robbery, after he learns the victim was his former girlfriend. He then becomes quite introspective as he realizes the impact his career has had on his personal life and decides to turn his attention toward a new woman.

An FBI investigation into a computer hacking scam that taps into a bank's system to gain access to the identities and financial assets of its customers becomes personal for Don and the Eppes family.

Don runs into Robin Brooks during an investigation concerning informants and a chess master.

Two rock climbers in possession of a large stolen diamond are killed, and Don and the team hunt for the murderers; Charlie considers whether he should have his FBI clearance reinstated.

When eight people, including two police officers, are gunned down in a coffee shop, Don and his team uncover a trail of blackmail, corruption and romance; McGowan expands his investigation of Charlie and Don.

The team sifts through various rumors about a controversial charity organization to find the guilty party after its office building is bombed.

Don turns to his newly found religious beliefs when he is forced to deal with an escaped criminal who is bent on seeking revenge.

When a case against a weapons smuggler falls apart, the team takes a closer look at the jury that heard the case, searching for signs of jury tampering.

The team gets a last minute tip that could exonerate a dangerous mob boss who is about to be executed; Charlie tries to help the CalSci basketball team break their losing streak.

Charlie meets his mathematical equivalent when lottery agent Jane assists in the investigation into a complex scam that involves thefts of unsold lottery tickets.

After Charlie and Amita get married and begin preparations for their London adventure, they put a slight hold on their wedded bliss when they assist the team in helping Don track down the whereabouts of his gun after it goes missing.