Your a Federal Officer playing Grand Theft Auto with the US Government as you back-up.
You get to shoot-up bad guys, do some very simply puzzles (seriously easy) and a few other things but unless you really watched the 24 series, then don't bother with this game. Go get GTA and imagine your saying "Federal Agent, get out of the car!" instead and you pretty much get the same experiance.
There where seriously a lot of things they could have done far better and I really wish they had, since the series is always really good. In short, the only memorable thing you will do in this game is steel the cars, shot and blow everything up and all as the famous Jack Bauer.