Amerchantmarineseamanisfoundmurderedandsuspicionfallsupontheoperatorofadime-a-dancehonkytonkjoint.Afederalundercoveragentisplantedintheplacetogatherevidence,andhesoonlearnsthatthediveisonlyacover-upfordiamond-smugglingactivities,andthatoneoftheoperation'shenchmen,whoishandywithaswitch-bladeknife,isthekiller.Beforetheycanbearrested,thehenchmankillshisbossandisshotwhiletryingtoescape.