[1] The film, shot in a semidocumentary tone, is loosely based on the real-life actions of Erwin "Machine-Gun" Walker, a former Glendale, California police department employee and World War II veteran who unleashed a crime spree of burglaries, robberies and shootouts in the Los Angeles area between 1945 and 1946.

[6] On a Los Angeles street, Officer Rob Rawlins, a patrolman on his way home from work, stops a man whom he suspects of being a burglar and is shot and mortally wounded.

Two police detectives, Marty Brennan and Chuck Jones, are assigned to catch the killer, Roy Morgan, a brilliant mystery man with no known criminal past.

Forensics specialist Lee Whitey matches the ejector marks on the casing to those recovered in the killing of Rawlins and the wounding of Jones, connecting all three shootings to one suspect.

Brennan then digs deeper and learns that Morgan once worked for a local police department as a civilian radio technician before he was drafted into the army.

The police carry out the raid that night, but Roy, alerted by his dog's barking, flees through the attic and uses the Los Angeles storm-drainage tunnel system as a means of escape.

Variety magazine issued a positive review:He Walked by Night is a high-tension crime thriller, supercharged with violence but sprung with finesse.

High-spot of the film is the final sequence which takes place in LA's storm drainage tunnel system where the killer tries to make his getaway.