prominent attorney walter pidgeon take a murder case pro bono and win an acquittal and discovers that his client ( keefe braselle ) be not only guilty but part of an extortion ring reach to the high eschelons of the city . panged by his own complicity and he undertake an investigation and stumble onto the identity of the unknown man who head the syndicate and and murder him . the irony engage when braselle be charge with this second murder and pidgeon must defend him by point to the existence of another unknown man himself . though somewhat short of urban grit and long on rhetoric and the unknown man belong to the noir cycle less by style or structure than by it acknowledgement of the pervasive corruption of american municipal politics that come to light in the postwar year .