Marjorie Burns and detective Jimmy Flavin travel to the remote Red Rock Tavern in order to meet a judge who will marry them. There they meet a group of jewel smugglers who have been called to a secret meeting by a man named Wentworth, who is late. When Harrison, one of the smugglers, is killed from a neck wound, the tavern's police dog is blamed, until another smuggler, Hughes, receives the same fate and Jimmy gets suspicious. Meanwhile, bars mysteriously descend over the inn's windows and the phone wire is cut. When Wentworth finally arrives, he denies having sent for the group, of which only Mason, Gloria and Bill remain. Mason is killed next, when the lights go out, and Jimmy, watching the dog, proves its innocence. When Marjorie finds jewels in Gloria's suitcase, she and Jimmy begin to suspect that everyone at the inn could be the murderer. Marjorie then sees Jamison, the innkeeper who is confined to a wheelchair, walk, and finds a wolf mask complete with sharp false teeth in his dresser. Jimmy forces Jamison's confession, which reveals the identity of the inn's owner: an inventor named Mr. Morgan, whom Wentworth had financed. Realizing Jamison has no motive for murder, and finding his wife missing, the group searches the basement, where they hear threats from Mrs. Jamison on a phonograph record rigged by Morgan. When Jimmy finds Mrs. Jamison's secret room and foils her scheme to murder them all, it is revealed that, years before, her sister had been framed for the smugglers' crime and had killed herself. With the case solved, Marjorie and Jimmy marry.