Stanley and Oliver are mousetrap salesmen hoping to strike it rich in Switzerland, but get swindled out of all their money by a cheesemaker. While working off their hotel debt, Oliver falls in love with a chambermaid, Anna, who in reality is a famous opera singer spying on her composer husband, Victor, while he works on his new opera. The boys are assigned to move Victor's piano to a secluded tree house, but become trapped on a rickety rope bridge high above an Alpine gorge when they're met halfway across by a gorilla.