Oh Dae-su is an ordinary Seoul businessman with a wife and little daughter. After a drunken night on the town, he is abducted and locked up in a strange, private "prison". No one will tell him why he's there and who his jailer is and his fury builds to a single-minded focus of revenge. 15 years later, he is unexpectedly freed, given a new suit, a cell phone and 5 days to unravel the mystery and discover the identity of the enemy who had him imprisoned. Seeking vengeance on all those involved, he soons finds that his enemy's tortures are just beginning.