Dr. Eugene Ferguson (Cary Grant), a renowned American brain surgeon, and his wife Helen (Paula Raymond) are vacationing in Latin America when a revolution breaks out. They are taken against their will to the country's dictator, Raoul Farrago (José Ferrer), who urgently needs a life-saving operation. Over the next few days, while Ferguson trains assistants for the delicate operation, he witnesses various acts of brutality by the regime, especially by Colonel Adragon (Ramón Novarro), but his Hippocratic Oath compels him to do his best. Roland Gonzales (Gilbert Roland), the rebel leader, kidnaps Helen to pressure her husband into making a fatal surgical "mistake." His message to Ferguson is intercepted by Isabel Farrago (Signe Hasso), the patient's wife, and the operation is a success. Helen is released unharmed when Farrago dies soon afterwards and his government is overthrown.