Amita receives an offer for an assistant professor position at Harvard University but is plagued by doubt as her relationship with Charlie is challenged and her career is in upheaval.

First appearance of: Diane Farr as Megan Reeves and Dylan Bruno as Colby Granger Don and his team are called in when a woman attempting to rob a jewelry store in Beverly Hills is shot by a security guard.

Along with David Sinclair and new FBI Agent Colby Granger, Don discovers a secret code during a raid and enlists Charlie's help to crack it.

A week-long series of counter-terrorism exercises are put to the test by Homeland Security officials (John Heard and Scott Cohen) in Los Angeles, but the first one is violated by someone who releases a potentially lethal gas in the subway system.

Guest stars include Lou Diamond Phillips in the recurring role of FBI fugitive tracker and sniper Ian Edgerton, as well as Connor Trinneer and Cynthia Preston.

Guest stars include Graham Greene, Reed Diamond, Michael Greyeyes, Clyde Kusatsu, Kate Burton and Lorraine Toussaint.

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

A DNA synthesizer with the capability of customizing diseases is stolen from the campus where Charlie teaches, and Don figures the thieves may be terrorists out to start or advance a bio-warfare program.

When an ATF agent is found dead amid questionable circumstances, Don demands to take on the case, which revolves around an elaborate bank heist, after he learns the victim is his ex-girlfriend.

After an unknown man opens fire in the FBI offices, causing carnage and destruction, Don and his team must investigate his motive and his connection to a dangerous arms dealer who is on trial.

An FBI investigation into a computer hacking scam, which taps into a bank's system to gain access to customer's identities and financial assets, becomes personal for Don when the Russian mob spearheading it comes after him and threatens the safety of Charlie and Alan.

Two women are found dead with an apparent drug overdose, in similar positions with a syringe in the left arm; Don suspects a serial killer.