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Brain surgeon Dr.  Eugene Ferguson and his wife Helen are on vacation in a Latin American country when a bomb, planted by revolutionaries against President Raoul Farrago, explodes at a jai alai game.  Fearing full-scale war, they soon decide to return to their ship, but are arrested on the way by Colonel Adragon.  He places them on a train, where they are treated like prisoners, but when they reach the palace of the President, his wife, Isabel Farrago, greets them warmly.

She soon reveals that Farrago suffers from a brain tumor and needs Eugene's expertise.  At the palace, they are kept under guard again, which frightens Helen and makes Eugene resentful.  Therefore, he is cold when he meets Farrago, who speaks at length about the childishness of his people and their need for strong leadership.  Eugene agrees to operate in a few days, in return for their passports, freedom to move around and a hefty fee, all of which he is granted.

That night the couple dines with American oil businessman Sam Proctor, who warns them to leave immediately because saving Farrago's life will make them very unpopular with the people.  Adragon follows them to a nightclub, where he beats a waitress and threatens to arrest many of the citizens.  Eugene, however, forces him to leave, endearing himself to the patrons.

Over the next few days, Eugene witnesses several examples of Farrago's tyranny over his army, church and people.  Eugene speaks his mind to the ailing president, who needs his help and so cannot complain.  One day Helen goes to church with Isabel and is mobbed afterward, causing a fearful Eugene to send her back to America on a train.

While Eugene tries to train his surgical helpers to perform brain surgery and Farrago plans an outside war that will stop his own civil war, revolutionary Roland Gonzales kidnaps Helen and sends a messenger with a letter to Eugene stating that he will kill Helen if the doctor heals Farrago.  The messenger, however, is a traitor who gives the letter to Isabel, so when the day of the operation arrives, Eugene works for five hours and saves Farrago.

Afterward he is granted his freedom and stops at a nightclub with Sam, who realizes something is wrong and brings Eugene to Gonzales.  Gonzales informs him that he has Helen, and Eugene flees back to Farrago just as the revolutionaries attack the palace.  As shots fly through the window at Farrago, he again tells Eugene how he must save his people from themselves, and then dies of a brain hemorrhage.  Gonzales bursts in and, believing Eugene has killed the president, sets Helen free.

In the streets, Gonzales speaks the same words the president had uttered about taming the unruly populace, and then is downed by a passing bullet.  He calls for Eugene to save him and Eugene stares at him, uncertain of how to respond.