When several dirty bombs are found on American soil, The Unit is deployed to find and diffuse. On the home front, the wives prepare for a wedding and a possible divorce.
Molly is kidnapped and used as bait, while Jonas is out of the country looking into a Russian terrorist cell.
A random incident throws Jonas and Bob's carefully planned mission into chaos.
When Sam attacks Bridget, the other members of the Unit must hunt him down.
The mission's plans go awry and Bob must run interference when Jonas and Mack are undercover to find the terrorists who killed the Vice President.
As the Unit fights to rescue Jonas's old friend, a broken helicopter gas tank and nearby guerillas impede their mission. Meanwhile, Tom goes to extreme measures to extract information from a recovering alcoholic whose husband may have been behind a terrorist attack.
Unable to communicate with the outside world, the Unit and their families must survive when a deadly gas poisons anyone in their community who steps outside.
The unit initiates a new team member while Jonas coaches his daughter Betsy, on how to respond to media questions about her kidnapping and rescue without blowing the cover story.
The President orders the unit to capture a Nazi war criminal from his hiding place and deliver him to The Hague. In Washington, Tom Ryan confronts his past when he is offered a promotion to General
Jonas and a seriously wounded Mack take refuge in a monastery where he is ordered to steal the monks' most prized possession. Back home, Bob is asked to perform a dangerous mission that will reveal the darkest side of his job to Kim.
Jonas plays a game of high stakes baccarat to win back the services of a CIA spy who has gone over to the other side. His success is also key in getting court martial charges against team member Bridget Sullivan dismissed.
Jonas and the team force a Department of Defense official to go with them on an assignment and experience the realities of war; A mysterious women shows up at Aerodyne headquarters. Kim is finally reunited with her kids.
The team's attempts to raid an anthrax lab are thwarted by an official from the Department of Defense (Michael McKean), who believes his high-tech intelligence is superior to field logic.
Jonas and the team must travel through enemy territory to bring a young bride to her groom, preserving a truce between two warring Afghanistan tribes; Kim and Bob try to expose a man who is linked to terrorists.
The team keeps trying to rescue Betsy Blane from Syrian captors; Mack has an opportunity to get revenge on Ryan for his affair with Tiffy.
The team travels to Iraq to save Jonas' daughter, who has been kidnapped; Col. Ryan must face the consequences for his adultery with Mack's wife.
Hoping to con a terrorist into exposing his accomplices before they escape, the team produces phony evidence of an attack.
A nuclear scientist insists on making a deal with the team before revealing information about an imminent terrorist attack on a major U.S. city; Kim, Molly and Tiffy are asked to work under cover with Jonas.
Bob and Mac both find themselves in trouble when they each take assignments undercover. Bob as a chemist who hides cocaine by converting it to paint and Mac as a fighter trying to bust an illegal betting ring.
While the Unit is investigating a man they believe to be smuggling nuclear weapons, they discover that he is also smuggling women.
The team follows a scientist who may have been targeted by terrorists, hoping to link those same terrorists to a presidential assassination plot.
While women are being secretly relocated and moved off the base for their own safety, Jonas and the team must unravel an assassination plot against the vice president and president elect.
