| Director | Louis Leterrier |
|---|---|
| Budget | $45 million |
| Box office | $50.9 million |
Bart, a vicious loan shark residing in Glasgow, uses his bodyguard, Danny, to attack non-complying debtors. Bart has raised and trained Danny to be an attack dog and uses a metal collar around Danny's neck to control him. Because Danny was raised to be overly docile and unobservant once the collar is on, he barely knows how to live as a socialized person, and the collar trick begins to fail due to its inherent limitations.
A crime boss invites Bart to an underground fighting ring hosting death matches, offering him hefty prize money in exchange for Danny surviving monthly fights. After Danny easily wins the first fight, however, Bart gets into a mishap with another mobster and is left for dead after a shooting. Danny survives and takes refuge in an antiques warehouse, where he collapses. Sam, a blind piano tuner, takes him to his home. Together with his stepdaughter Victoria, Sam nurses Danny back to health. Danny slowly learns to be civilized and abandons his violent nature under their kindly care, even after Victoria removes his collar. He also curiously develops an interest in music and begins using scattered memories to remember his past, particularly his mother.
Weeks later, Sam informs Danny about moving back to New York, where he and Victoria are originally from. He invites Danny, telling him they think of him as family, who happily accepts. However, while out shopping alone, Danny runs into Bart's right-hand man Lefty, who reveals Bart survived. Lefty takes Danny back to Bart; Danny asks Bart if he knew Danny's mother. Bart denies knowing her and takes him back to the underground ring for their next fight. Initially overwhelmed by his four opponents, Danny eventually defeats them, but refuses to kill. Livid, Bart drags Danny back to their compound and throws him into his cell. However, Danny sneaks out and looks through Bart's old photographs, finding one of a person who looks like Danny's mother. Bart insists that his mother was a prostitute who disappeared after abandoning her son.
Danny escapes the next morning and goes back to Sam and Victoria, telling them where he was and what he has learned. With the two's help, Danny regains his childhood memories: his mother was a music student in Glasgow struggling financially, so she offered herself to Bart for funds, while hiding a young Danny in the closet. It ended when Bart shot her to death when she finally defied him, and Bart has raised Danny ever since.
Bart and a group of thugs arrive at Sam's apartment complex to capture Danny. Danny hides Sam and Victoria in their closet and goes out to fight them off. Danny confronts Bart, who implores Danny to abandon his new life and come back to his old one. Danny refuses and furiously beats Bart. Sam and Victoria burst out and beg Danny not to kill; however, a defeated Bart orders Danny otherwise, and taunts him. Sam smashes a flowerpot on Bart's head, knocking him unconscious. Sam, Danny, and Victoria embrace.
Sometime later, Danny is with Sam at a piano recital at Carnegie Hall, where Victoria begins playing. She performs the same song from Danny’s childhood, prompting Danny to smile.