Geeky teen Dave Lizewski decides to become a superhero, even though he has no super powers, training in martial arts or any good sense. Donning a vintage wetsuit and heading out onto the streets 'Kick Ass' becomes an internet sensation after footage of him stopping a mugging - and subsequently getting beaten up - is posted on YouTube.

Soon his antics bring him to the attention of the city's criminals, eager to stamp out the vigilante, and it isn't long beofre he crosses paths with several other costumed crimefighters who were inspired by his mission.