Basically, it takes place in Chicago. Jack is living in pretty bad conditions. He is waiting on someone and notices a person on a motorcycle watching him. Chloe arrives and they talk for a minute. She tells him that someone hacked her system and accessed all of the info on his autopsy. Chloe fears that the person who did it will figure at that Jack is alive as they were so good that Chloe couldn't trace them. Then she says "I can't believe you have to live like this" and is clearly hurting for him. They depart, Jack asks her how Kim is and Chloe says she was devastated but is better now. Jack takes the cell phone Michelle gave him at the end of Season 4 and trashes it.
As he prepares to drive off, a car comes up behind him and the chase is on. After a car chase, Jack manages to dispatch the bad guy in typical Jack style. He drives off with the guy on the motorcycle still watching him.
Season 4 is 6 discs for me. Is the Prequel a 7th disc?