With a life-and-death hostage situation paralleling own strange circumstances, Sam Tyler is ordered with the rest of the 1-2-5 to diffuse a potentially deadly face-off at a hospital where a crazed gunman is trying to force a doctor to reverse a dangerous operation on the renegade's brother, and the squad are all targeted in the gunman's cross-hairs.

The detectives at the 1-2-5 investigate the murder of newspaper journalist Joey Conway. Sam is convinced the killer is the same criminal from a case in 2008. He is motivated by flashbacks to the case, which puts him at odds with his coworkers who think someone else is guilty.

When a Pan Atlantic air hostess is found dead, Annie volunteers to go undercover in order to solve a series of homicides. Annie, Sam and Ray, working undercover, are able to find an unlikely suspect.