Something 'awful' has happened that has made Alex Mercer one of the most powerful shape shifter on the face of the planet. Naturally, instead of rejoicing, he has sworn to get to the bottom of this, find out who did this to him and destroy him. So this translates into Mercer obliterating a vast line of armored vehicles, helicopters, military bases, buildings, super soldiers and of course, the infected.
You are thrown into the middle of the action at once and the adrenaline never lets up throughout the game. Unfortunately, the same cannot be said about the feeling of invincibility bestowed upon you at the start of the game. Very quickly you realize that if you don't act sharp, then you will be killed. Although a little inconsistent, this was necessary to create an environment with a strong sense of urgency and danger.