A story of Ralph Lindsey's undercover work nabbing a car theft ring in a small Massachusetts town gives the road to the realistic approach. Facts: cop covers as tough teenager, gets mechanic job with suspects, is recognized by youth who wants out but is murdered by big man, springs trap around terrorized girlfriend of big man and barely manages to pull himself out --major repair job postpones his marriage but he feels the compensations (fried gang, free girl) worth it. Substantial middleweight fare.