Assistant DA Bob Martel (Bruce Cabot) is in love with sweet Muriel (Mary Brian). This in itself is not earth-shattering, except that Muriel is the sister of gangster boss Rossi (Harry Woods). The latter frames Martel for murder, but the police forensics lab provides a surprising solution to his plight. Columbia Pictures' standing prison sets, originally built for The Criminal Code, are given a good workout here. Grant Mitchell gives the best-rounded performance as Martel's father, who expedites the film's satisfying conclusion.