The story begins with the theft of a device capable of controlling time. Before his escape through time, the thief destroys the lab. Rather than die in the ensuing explosion, you decide to take your chances with S.S.A.M., a suit that can also manipulate time. You are immediately pulled into the 1940's, where WWII should be in full swing. Instead, you are greeted with something that looks more like the future from
Terminator. Whoever took the first suit has messed with time and used his knowledge to take over the world (don't they always).
As is usually the case with time travel, the story is incredibly confusing at the start; there are several blanks left to be filled in and no one really knows what is going on. The more you play, the clearer things get. This isn't to say that it makes a whole lot of sense then, but as far as these types of stories go it works - especially since it leaves you just enough room to imply what is going on rather than have everything explained.
What isn't as confusing is the gameplay, which is pretty standard when it comes to first-person shooters. What isn't standard are the time controls, which have just as big a role in the game as gunplay. As the game progresses, you'll use these skills in different ways. The first, and most entertaining, use is the ability to stop time and steal weapons from enemy's hands. At this point, you can either shoot them with their own weapons or watch their reaction when they realize they are unarmed. Eventually you'll learn to reverse time, which comes into play when solving puzzles.
Online is one of TimeShift's better features. I would even go so far as to call it the game's best feature. Rather than giving you full scale control of time, you instead use time grenades to mess with other players. Once activated, time grenades create a sphere of influence that manipulates time for whoever is stuck inside. This opens up some really cool strategic options, such as throwing a reverse grenade and having a rocket returned to sender. Traditional multiplayer stand-bys like Capture the Flag are included and joined by modes like Meltdown Madness, which involves using time powers to speed up and slow down reactors. There's also a King of the Hill variant where the "it" person has control of time powers.