A town is being terrorized by a masked killer who is murdering women. A young woman is attacked by the killer but escapes. She believes the killer to be either the town's policeman or the manager of the local theater, and she devises a plan to find out which is the actual killer.。“黑脊背”武艺高强,却身有残疾。同乐班的青年寇元庆为人仗义,爱打抱不平。元庆不会武功,却常冒名大刀客“黑脊背”去行侠,又在真“黑脊背”的暗中帮助下屡屡得手。后来俩人双双遇难。。