The Fat Man is a 1951 American film noir crime film directed by William Castle. It is based on a radio drama of the same name, with J. Scott Smart reprising his role as Brad Runyan, a portly detective.
Portly private detective Runyan is asked by dental nurse Adams to investigate the unexplained murder of her boss. Suspicion falls on disappeared patient Clark, last seen being driven from his appointment by the chauffeur of probable gangster Gordon. Through his means, Runyan contacts Boyd, Clark’s former lover and briefly his wife, who reveals that Clark had once spent time in jail. The police tell Runyan it was for robbery of half a million dollars which were not recovered. In jail, Clark had a cellmate Deets, a circus clown, with whom he shared everything. On release, Deets had claimed Clark’s share of the loot from Gordon, the heist‘s organizer, in order to fulfil his ambition to own his own circus.
Deet’s side of the deal was to eliminate Clark, whose corpse he left in a burnt-out truck. When he realised Clark had undergone dental treatment, and that this meant Clark could be identified by dental records, Deets killed first the dentist and then Nurse Adams as well. Runyan locates Deets, and in a final shoot-out, Deets is fatally wounded and dies in his own big ring.