Private detective Mariel Adams is approached by young designer Sophia Robins, who discovered the corpse of an unknown person on the threshold of her apartment. The murdered man turned out to be Gregor Shine, who had just served seven years for stealing a unique collection of pearl jewelry from the late Anthony Kranz. Only the most valuable exhibit was missing from the collection - a ring with a black pearl. According to legend, the ring brings good luck to those who manage to steal it.