After being put on suspension at the LAPD, Mike Carter punches Lieutenant Borden and quits in disgust. A few days later, at a baseball game, he is approached by Fred Dysen, who wants to hire Carter as a bodyguard for his aunt, Gene Dysen, a widow and head of Continental Meat Packing Corp. Carter refuses. Later, at his apartment, an envelope slips under the door containing $2000; Carter races outside, but the person who left it is already gone.
[Carter] then drives to the Dysen mansion in Pasadena, pushing his way in and, after meeting the household, finding that Mrs. Dysen is uninterested in a bodyguard. He returns the money to [Fred Dysen], but just as he is leaving, someone shoots at Mrs. Dysen but escapes. After she goes to bed, Fred convinces Carter to stay the night, and Carter takes back the money.
At 3:45 am, Carter catches Mrs. Dysen's secretary, Connie Fenton, digging bullets out of the wall, then sees Mrs. Dysen drive away. He follows her car to the Downtown Los Angeles warehouse district, where he is knocked unconscious, waking up later in his car with [Lieutenant Borden] shot dead beside him, on the railroad tracks with a train bearing down. Carter barely escapes.
Realizing he is being framed for the murder, he asks his fiancée, Doris Brewster, who is Lieutenant Borden's secretary, to dig into the cases Borden was working on. She drives him to the Dysen home; Mrs. Dysen is not there, and he finds she is also absent from the plant.
In the files on Borden's cases, one item stands out: the death of inspector Alex Stone at the Continental Meat Packing plant. Back at the Dysen mansion, Carter confronts Mrs. Dysen about her movements that morning. After she offers a plausible explanation, he asks Doris to bring more information on Stone's death. He also speaks with the dead man's brother Adam, who recognizes Carter as someone the police are after. Carter discovers evidence that Stone's claim of faulty sight may not be accurate after all.
Narrowly avoiding arrest, he visits the optometrist Dr. Briller and then breaks into the glasses manufacturer to obtain the needed information. He calls Captain Wayne to meet him at the Dysen home. Meanwhile, Doris spies on Fred and Fenton, the plant supervisor, at the factory.
At the mansion, Carter confronts Mrs. Dysen, who reveals that Freddie thinks [Fenton] has been adding water to the meat to inflate profits and pocket the difference. Stone was murdered to cover it up. Carter concludes that Fred is in cahoots with Fenton on the fraud. Doris, meanwhile, is in danger at the plant, prompting Carter to steal a police car and hurry to the plant.
At the plant, Fred explains how he intends to frame Fenton for the deaths and exonerate himself, with Fenton dead. Carter arrives just as Fred is about to shoot Doris; after Fred runs out of bullets, Carter fights and knocks him out. The police arrive and take Carter and Fred into custody. The final scene shows the newlywed Mr. & Mrs. Mike Carter heading off for their honeymoon in a police cruiser.
