In 1861, Scottish immigrant Allan Pinkerton (Christopher Reeve) is designated head of the Secret Service after thwarting an assassination attempt on newly elected president Abraham Lincoln. Later, Pinkerton, on a counter-espionage assignment for the Union, falls for comely southerner Rose O’Neal Greenhow (Madolyn Smith Osborne), who he suspects is a Confederate spy. Events take an unexpected turn when the reluctant lovers unwittingly become co-conspirators.