Roger Quain (Howard Duff) arrives in Europe to look after the welfare of two zoo-bound black panthers. Catherine Ulven (Marta Toren), a secret agent for an unnamed country, decides to smuggle a valuable piece of film to America by hiding it in the collar of one of the big cats. If it were this easy, the film would be over in ten minutes. Instead, enemy agents Denson (Philip Friend), Paradou (Robert Douglas) and Kopel (Dorn) target Roger, Catherine, and the panthers for extermination. Thus the stage is set for a thrill-packed pursuit through the mountains of Switzerland. Spy Hunt is based on the somewhat more credible novel Panther's Moon by Victor Canning.