Who better to guard a priceless pearl necklace than an ex-thief? That's the logic behind Trapped by Boston Blackie, starring Chester Morris in the title role. Blackie finds himself posing as a guard at a society party, where the hostess (Sarah Selby) intends to display her new necklace. The private eye officially assigned to guard the pearls is mysteriously killed (or so it seems), whereupon the necklace vanishes. Blackie must locate the real crook before the cops arrest him on suspicion. Trapped by Boston Blackie was the twelfth in Columbia's "Boston Blackie" B series.