Jimmy Valentine
Jimmy Valentine is the story's enigmatic protagonist. A notorious and highly skilled safecracker known to law enforcement as Prisoner 9762, Jimmy's kindness, youthful appearance, and good nature garners people's trust. He has no apparent interests other than opening safes until he falls in love with Annabel Adams. For the second half of the story, Jimmy invents a new identity as an honest man, becoming Ralph D. Spencer, a shoe shop owner.
Annabel Adams
Annabel is Jimmy's fiancée and the daughter of Mr. Adams, who owns the Elmore bank. Annabel is bashful and fun-loving. She knows nothing about Jimmy's life as a criminal, nor his real name.
Agatha
Agatha is the five-year-old daughter of Annabel’s sister. Her older sister May accidentally locks Agatha inside the bank vault, which Jimmy eventually opens.
Ben Price
Ben Price is the police detective who first put Jimmy in prison and who later tracks Jimmy to Elmore. Ben works the case slowly but thoroughly. At the end of the story, Ben decides not to arrest Jimmy, having seen that he is a reformed man.
May
May is the nine-year-old daughter of Annabel's sister. While playing, she accidentally traps her younger sister Agatha in a bank vault.
Annabel's Sister
Annabel's sister brings her young children for a tour of the Elmore bank toward the end of the story. She panics when her daughter Agatha becomes trapped in the vault.
Warden
The prison warden lectures Jimmy before Jimmy's release. The warden believes Jimmy has a good heart and asks him to consider making a new start as an honest man.
Mike Dolan
Mike Dolan runs a café, above which Jimmy has a room. Mike Dolan helped free Jimmy from prison and is part of Jimmy's network of criminal accomplices. He is friendly to Jimmy and amused by Jimmy's seemingly insatiable need to open safes.
Billy
Billy is Jimmy's criminal acquaintance. Jimmy writes a letter to Billy saying that he would like to give Billy his safecracking tools; he also needs Billy to tie up some loose ends in Jimmy's old life.
