Death Trap, originally published in 1957, is one of John D. MacDonald's best stand-alone thrillers.
Hugh, a globe-trotting construction bum, spots that an ex-girlfriend's younger brother is about to be executed for murder. He is drawn back to a small Anytown in the hopes of helping his ex-girlfriend, Vicky, through the trauma - and also to ease his own troubled conscience.
Hugh invariably gets tangled up in detective work. Initially, he makes a haphazard effort to placate Vicky, but soon discovers that this small Midwestern town has a seedy underbelly.
It also, in the best JDM tradition, has a violent deputy and a politically-minded sheriff, neither of which encourage Hugh's amateur investigations.
Hugh's efforts lead him into the depressing swamp of small-town juvenile delinquency and the frighteningly rigid adult system that created it. Hugh's interactions with the town's sordid teen populate - and its deliberately-blind authority figures - are the highlights of the book. With his outsider's point of view, Hugh can see that the town is built on lies, desperately painting over the corruption to preserve the status quo.