Soldiers-for-hire Baldwin and Dugan (Vinton Haworth and Gordon Jones) land a perilous assignment -- ensuring the safe arrival of the priceless Soo diamond to a shop in Shanghai. Upon delivery, the shop is attacked and in the ensuing firefight, the diamond disappears. Aided by the local authorities, the two round up a motley crew of six unusual suspects, all found in the Chinese quarter late at night -- attractive and uncooperative Jane Dunn (Constance Worth), inane Mrs. Katie Collins (Joyce Compton), dipsomaniac Philip Burton (Dick Elliot), mystery writer Anthony Durand (Leslie Fenton), Durand's British valet Harvey Dinwaddle (Alec Craig) and the mysterious Dr. Fang Tu (Philip Ahn). The tables of suspicion are turned when all concerned board the same ship sailing to America. As the bodies begin piling up, Jane Dunn turns out to be an undercover agent, while Baldwin looks like a cold-blooded killer!