Working the night watch out of homicide, Joe Friday takes the phone call reporting two police officers shot. He and partner, Ben Romero respond, and interview the police on the scene. All 23 men from the cafe are rounded up and interviewed, and a red headed gunman is agreed up on as the shooter. Joe, Ben, and chief Backstrand are all concerned as their fellow officer undergoes surgery.
Using the high technology of an IBM computer with punch cards, records are sorted through to arrive at a couple key suspects. Amazing how much information you can get from those little punched out holes on those cards. More interviews at other crimes seem the same, but descriptions of the men don’t match. Is one shooter a red head, or not? A left handed shooter, or not? A lucky taxi driver tells what he knows, but the leads are taking the cops nowhere fast. More cab drivers are shot, and the only consistency is the weapons being used.
Mapping out the area where the shootings took place inspires a blockade, and the hope of trapping the killers. The overworked cops get some rest, then with a fresh look at new clues, progress is made. Working with a few names of possible criminals, a burglar is picked up who matches one, and lives in the neighborhood. Is this the break Joe has been looking for? The floodgates open, and soon all the gang is in custody, and the story behind how their scam worked to confuse the cops.