In a San Francisco train yard, photographer Jack Early hides a camera just before he is beaten by some men who are chasing him. Later, he retrieves the camera and takes the pictures to newspaper photo editor Ellen Bennett. She agrees to buy one, but Jack refuses to sell it unless they hire him for a week, at the end of which he vows to prove his worth. Reluctantly, managing editor David Glover agrees to his terms and then assigns him to photograph lost and found dogs. At the end of the week, Jack has dinner with Ellen, and as he leaves her apartment, his cab almost collides with a drunken driver. Jack orders the cabby to follow the car, and when it falls off the road into the water, Jack persuades the drowning driver to pose for a picture before running off without saving him. Later David politely suggests that the next time Jack happens on a good shot, he call the paper so that they will have a story to go with his picture. Jack then steals another photographer's tip and gets a spectacular shot of a fire. Although David is skeptical of Jack's story that he just "happened" to be in the neighborhood, he gives Jack an assignment to photograph elegant racketeer Nick Palmer, who has been careful not to reveal his face in public. Jack completes the task by flattering Palmer and then asking him to pose for the shot. Although David continues to dislike Jack, he nonetheless puts him on staff. In the meantime, Ellen, who is engaged to a Portland, Oregon dentist, has fallen in love with Jack, unaware that he is just using her. Jack proposes a system of reciprocal favors to Palmer, who suggests that Jack help him frame rival gangster Colton. Acting on a tip that Colton is going to rob a local department store, Jack waits outside and photographs Colton and his men as they leave the store. He gives Ellen a picture that does not reveal the identity of the men, then hides a shot of their faces and a negative behind the framed photograph of her fiancé. Later, he blackmails Colton, and when he discovers Colton and his men searching his apartment, reveals that Palmer informed him of the robbery. He then tells Palmer that Colton plans to shut down one of his places. When Palmer leaves the room to make a telephone call, Jack kisses Palmer's beautiful young wife Nita, who tells the disbelieving Jack that she loves her husband. One evening Palmer asks Jack to come by the apartment. His urgency leads Jack to suspect that Colton has threatened Palmer's life. He waits outside Colton's bowling alley headquarters and follows his men to Palmer's apartment building. He then hides in the garage and photographs first, the men placing a bomb in Palmer's car and later, the explosion that kills him. The picture makes Jack famous, but David again does not believe his explanation that he "happened" to be in the garage. When Jack learns from Ellen that he has received lucrative magazine offers, he quits the paper, even though his leaving means that David might lose his job. Jack continues to pursue Nita, who accepts his expensive gifts, but otherwise treats him rudely. When Jack is assigned to photograph a society ball at the Worthington house, he uses the picture of Colton's men setting the car bomb to blackmail him into robbing the house and splitting the proceeds. After he leaves, Colton visits Nita, who is still devastated by Palmer's death, and tells her that Jack killed her husband. Together they devise a plan to kill Jack. At the ball, Nita pretends to accept Jack's marriage proposal and then accuses him of Palmer's murder. To disprove the allegation, Jack calls Ellen and begs her to bring the photograph to the house. Ellen, who has finally put Jack out of her life, refuses. Jack then wrestles the gun away from Nita. Colton fires, hitting Nita, then Jack. Just before he dies, Jack pulls the cord on a camera, which is already set up, and captures his own murder on film.