George McCabe, an infamous criminal who commands respect and fear, is arrested during a botched diamond heist and locked up at Braintree Prison. Lawrence Nixon, a struggling actor battling to keep the bailiffs from his door, is about to get the biggest break of his career. As the spitting image of McCabe, Lawrence is to star in a TV reconstruction of the heist. Unfortunately Lawrence is not a great actor, and decides to liven up his performance with a lisp and camp walk, rendering McCabe a laughing stock among inmates. Desperate for revenge, and spurred on by the discovery that his girlfriend, Cassie, is about to publish a warts-and-all book about his life (which would mean certain death for him), McCabe devises a plot to escape and sort things out. Lawrence is kidnapped and forced to trade places with McCabe in prison. The swap is a success but no one could predict the life changing effects this unlikely switch has on the two men.