“Howard Duff has picked up a couple of black panthers — the animal kind — which he is delivering by train to a circus in Germany. Little does he know that spy Märta Torén has hidden important microfilm in one of their collars. Other spies have gotten wind of this, so they derail the railroad car he is traveling in with the beasts, sending him tumbling down a Swiss mountain. When he awakes, he is in a hotel being tended by the owner, Doctor Walter Slezak, and various characters, all made suspicious by their non-American accents are showing up. Are they there for a newspaper story, or to sketch the beasts, hunt them, or to get the microfilm?”