Pat Allen, a Daily Sentinel reporter, is mysteriously killed by a leopard. While cleaning out his desk, Britt Reid discovers a large diamond that turns out to be a perfectly-manufactured fake, and wonders if Allen uncovered something bigger than he expected. He also finds a transmitter that emits a supersonic tone - the type audible to cats. Britt Reid suspects the leopard must have been trained by someone to kill at that signal. Donning his Green Hornet gear, he sets out to visit Frank Miller, a shady gemologist, for clues leading to Pat Allen's death.
