Eighteen months have elapsed since the conclusion of Day 3. A commuter train bound for Los Angeles explodes. A man steals a suitcase from a passenger in the wreckage and then kills him.

Jack has been dismissed from CTU and now works for Secretary of Defense James Heller. Jack is involved with Heller’s daughter, Audrey, and their relationship is growing serious. Jack is in LA for a meeting with CTU Director Erin Driscoll, who fired him a year ago, but he finds himself alienated at CTU by Driscoll and the new staff when reports of a possible terrorist strike come in.

A young computer hacker named Andrew Paige sees something that he shouldn’t on the Internet. Suddenly, he finds himself running for his life as he is pursued by terrorists. Luckily, he is able to warn Chloe O’Brian before its too late.

The Turkish Araz family are not what they seem and it becomes clear that they are heavily involved with the day’s events. Meanwhile, Heller has a confrontation with his estranged son.

Jack finds that Chloe is his only ally as he tries to prove that the train explosion is merely a diversionary target.

It’s Halloween and reaper legend has it that the reapers can be seen as they were when alive. A serial killer stalks a neighborhood, the reapers collecting his victims as he goes, George getting the bad guy. Joy and Reggie pay a late night visit to George’s grave. So does George.

George finds out that her mother was in Happy Time looking for her file. Rube goes to see his daughter after receiving upsetting news from Penny. Ray continues to cause problems even after his death and Mason runs into a bit of trouble with Kiffany.

Mason and Daisy try to keep Ray’s death a secret. Mason receives a purple post-it, possibly his final reap before moving on. Roxy investigates Ray’s disappearance, questioning Daisy . George attends another going-away party at Happy Time. Reggie accidentally lets J.D. out, and searches for the dog.

The hockey game rematch between the NYPD and the FDNY is right around the corner and Tommy must figure out a plan to save himself from being pummeled by the cops who have it out for him. Tommy’s relationship with Sheila is discovered by the guys and they must adhere to tradition to handle it in their own way. When Tommy is visited by his demons during a fire, Franco comes to his aid… with devastating results.

Ray and Mason fight for Daisy’s affection, and their game turns into something worse when Daisy wants to breakup with Ray. In a hospital, George must convince an elderly woman of her death. Joy is looking for a job at Happy Time, where she finds out more information about the time George worked there. Rube seeks help from Penny, another reaper, to find his daughter.

George tries to pass herself off as the relative of a homeless man, while Daisy performs as a temptress on Ray’s reality show – much to Mason’s disgust. Reggie, meanwhile, tries Goth on for size.

While Tommy attempts to make reason of the chaos in his life, he continues to defy death while pulling dangerous stunts on the job. Lou admits his infidelity to his wife and receives an unexpected surprise. When tragedy strikes his family, Tommy must come to the rescue of his father.

George is in a foul mood, after Trip. Daisy makes a new friend which makes Mason jealous. Rube leaves, looking for a mysterious woman from his past.