An eccentric millionaire, Cadmus Cole, visits the newly-founded offices of Ellery Queen, Confidential Investigations, in a rare incidence of disembarkment from his yacht. The investigation company is actually the brainchild and sole responsibility of his partner, "Beau" Rummell, an established private eye. The eccentric Mr. Cole pays $15,000 as a retainer to hire Ellery Queen for an investigation -- the details of which he refuses to divulge, saying only "You'll know when the time comes." Upon his departure, he leaves behind a well-chewed fountain pen with which he's signed the retainer cheque. Almost immediately, Ellery's appendix bursts, and Cadmus Cole is reported dead and buried at sea. Rummell, in the guise of Ellery Queen, begins to investigate both the circumstances of Cole's death and his heirs; he soon meets two beautiful young women and the case becomes complicated by romance and the appearance of a claimant under the will. When the claimant is murdered, and Rummell married to one of the beauties, the real Ellery Queen must take a hand and solve the case, using the vital clue of the chewed fountain pen.