"Papillon", un hombre condenado por asesinato, es enviado a un penal de la Guayana francesa. Durante el viaje en barco, conoce a Luis Dega, falsificador de Bonos de la Defensa Nacional, un hombre débil, al que "Papillon" ofrece protección a cambio del dinero que necesita para huir de la cárcel.
La señora Lowe (Ann-Margret), una atractiva viuda, quiere recuperar el medio millón de dólares en oro que su difunto marido robó durante el asalto a un tren. Lane (John Wayne), atraído por la recompensa que ofrece de 50.000 dólares, decide ayudarla. Para ello cuenta con la colaboración de unos amigos.
Ambrose C. Park, left on a park bench as an infant with an impulsive need to find his parents, is an assistant to a diamond cutter. Shyster lawyer Remlick, in a strategy to get a fabulous uncut diamond through Ambrose, arranges for Emily Drummon, Duke Fargoh and Maggie Drummon to pose as Ambrose's long-lost parents and sister. The diamond, through many comic situations, is acquired and the gang is going to have Ambrose cut the diamond, and relieve him of the two stones and his parental illusions at the same time. But Maggie, who has no taste for the deception, tips Ambrose off and a wild chase ensues. At the end, Ambrose is very happy as he can now marry his "sister."
