As he's conducting investigations into murders and robberies Sam Tyler is also continually dealing with coming face to face with his "past". In various episodes over this first season he meets his mom, hears the voice of his younger self once or twice, and, finally, his father is a suspect in the final episode of the year. Sam "remembers" his dad mysteriously vanishing when he was young, and as the episode unfolds he realizes that he is not only going to be solving a crime but is about to discover what happened to his father all those years ago. Near the beginning of the case he latches on to the hope that maybe this is the reason he's been sent back into the past - to prevent his dad from leaving - and perhaps if he can do that he'll be able to go home. Back to the present.
Each of the fours discs are in widescreen format and come with optional cast and crew commentary. There are also various special features scattered throughout the four disc set including a very good two part documentary about the making of the series that includes interviews with the writers, producers, and cast members. I'd advise not watching it until after you've watched the series so as not to ruin any of the surprises in store during the show.
Life On Mars does an amazing job of weaving together the three story lines; the clash of police techniques, the actual investigations themselves, and Sam's quest to understand just what the hell is going on with him. A combination of great writing, even better acting, and a refusal to either glamourize the violence of the 1970s' coppers or make Sam's character a saint, make it not only a great police procedural show that's surprisingly funny, but also amazingly credible. With the action being so believable, it becomes even more difficult to understand what Sam is actually going through and by the end of Series One we aren't that much the wiser. Life On Mars: Series One is as marvellously produced piece of television as you're going to see in a long time and leaves you definitely wanting more.