On the day Jimmy Valentine is to hand over the tools of his former trade to an acquaintance, the reformed thief finds himself in a quandary.
While everyone is admiring the bank's new vault, little Agatha is playfully locked into the safe by her older sister, May. Agatha is only five years old, and she is terrified of being locked in the dark. Furthermore, with limited oxygen, Agatha's life is in danger. For security purposes, the vault will only open at a time set by a special clock, and since Mr. Adams has not yet set the clock, opening the door of the bank vault will not prove an easy task.
Jimmy Valentine has a hard choice to make: he either saves his future niece by marriage and risks unmasking his true identity to the plainclothes officer at the bank or lets little Agatha die a painful death. Eventually, his love for Annabel wins out, and he resolves to once more use the tools he has vowed to give up, this time for a different purpose than what they were designed for. Jimmy's skill with safe-cracking is evident because it only takes him about ten minutes to free Agatha. Satisfied that he has been able to do a good deed with his old tools, Jimmy turns to surrender himself to Ben Price, the police officer. However, Ben mysteriously pretends that he does not know who Jimmy is.
The story ends with Ben leaving the bank without having apprehended the elusive, former thief. It is possible that Ben refuses to arrest Jimmy because Jimmy's actions prove that he has changed. The once sly and dishonest thief no longer seems to be solely concerned with increasing his material gains at the expense of his unsuspecting victims. The fact that Jimmy chooses to expose his true identity in order to save the life of an innocent little girl speaks volumes about the change in his character. Satisfied with everything he has observed, Ben Price chooses to leave Jimmy to his new life.