Plunder of the Sun

Plunder of the Sun is a 1949 novel by David F. Dodge about a hunt for ancient Peruvian treasure. It was adapted into the November 8, 1949 episode of the radio series Escape and later into the 1953 Film Noir movie of the same name starring Glenn Ford with the location changed to Mexico.
Plot.
The adventurer Al Colby is persuaded by Anna Luz and her antiquities collector husband, Thomas Berrien, to help them smuggle a parcel back into Mexico where its true value can be ascertained.
Warned that a man named Jefferson traveling on the same freighter might try to steal it, Colby ultimately forms a partnership with Jefferson following the fatal heart attack of Berrien aboard ship. Jefferson betrays and shoots him, but Colby saves himself and the rare documents in time. They will be returned to a museum while he and Anna can enjoy a $25,000 reward.