Some dastardly criminals have stolen some top secret plans and tattoo them on the back of a woman so she can sell them to the highest bidder in Lisbon. This woman plans to take the place of a 'Sidney Royce', a legitimate traveler going to Lisbon as a reporter. Crossed signals allows the real Sidney to reach Portugal first, where she is pursued by those trying to obtain the plans and US government agents trying to prevent the sale.