During the day, Arthur Poppington (Woody Harrelson) is a normal man (even if slightly naive to the workings of the world) working in the construction industry. During the night time, he transforms into his alter-ego, Defendor, protecting the streets from thugs. The city has a problem with thugs and nobody is prepared to stand up and fight for themselves. The police are slow to catch the wrongdoers and Arthur has a huge willpower to do what he can to help the people. He helps Kat (Kat Dennings) one night from Dooney - when she really didn't need any help - she was a hooker. Dooney (Elias Koteas) is a corrupt cop in the police force and he is in cahoots with a Serbian mob boss. Arthur has been searching for Captain industry all his life as he had killed his mother. Kat and Arthur become friends and Defendor goes after Captain Industry knowing that there is a very high chance of dying or getting arrested.