An aging never-was actor, Anthony O'Malley (Michael Caine), convinces his young colleague and cast mate Tom (Dylan Moran) to hone his craft by playing a character in real life. Tony suggests killing two birds with one stone, by impersonating a London gangster and claiming a debt owed by a retired gangster named Barreller (Michael Gambon). Everything goes according to plan, until Barreller's daughter Dolores (Lena Headey) falls in love with Tom’s imaginary persona.