Ex-Army officer Jameson takes a job a prison guard at San Quentin. Joe, the brother of his new girlfriend May, is sentenced to the prison for robbery. When Jameson tries to separate lawbreakers from hardened criminals, badguy Hansen tries to stir up trouble by telling Joe about Jameson's interest in his sister. Written by Ed Stephan

Television viewer seeing this for the first time: Gee whiz, it's in black-and-white and was made in the 40's and is about crime and...Eureka!...another "noir" film is discovered. How about just another typical Martin Mooney film that starts out as pretending to be something socially significant---call Prison Warden Lewis E. Lawes to do another prologue speech---and then quickly gets into just another cops-vs-robbers (or good crooks vs. bad crooks)B-feature action-thriller that will open in every 2nd-tier theatre in the country on Sunday, close on Wednesday... and be the bottom-half of a grind-house twin-bill two weeks later. "San Quentin" ably fills that description. Ex-con Jim Rowland (Lawrence Tierney), gone straight and returning from WWII as a hero, is more than a bit irked, as one of the founders of the Prison Welfare League (cons rehabilitating cons inside and outside the walls), when he learns that bank robber Nick Taylor (Barton MacLane) has used the good name of the PWL to escape from San Quentin, and knocked the Warden in the head to boot. This is one founding father that isn't going to stand idly by after the good name of the PWL has been stained, especially by the likes of Barton MacLane, probably still laughing at the thought there was a Warden somewhere who would actually trust him. So Jim and his ex-con pal 'Broadway' (Joe Devlin) set out to track down Nick Taylor. They encounter Marian Carr along the way. Written by Les Adams