 When Mrs. Tremayne is mysteriously poisoned with gas, ambulance driver Frank Jessup meets her refined but sensuous stepdaughter Diane, who quickly pursues and infatuates him. Under Diane s seductive influence, Frank is soon the Tremayne chauffeur; but he begins to suspect danger under her surface sweetness. When he shows signs of pulling away, Diane schemes to get him in so deep he ll never get out.