A big bomb goes off in the city and destroys half the people or so. There's a plague and the government quarantines you in. You wake up with lightning bolts coming out of you (literally) and you have to figure our what happened, but you can jump off buildings, do neat acrobatics, and you gain power from electricity. It's like a more structured GTA without the ability to fuck and you don't use guns.
I wouldn't have purchased it if I didn't get it for free, but I gave it a shot and its kind of fun.