News correspondent Tim Garnett (Stephenson) and his photographer Connelly (Richard "Skeets" Gallagher) have been on assignment in a country on the edge of revolution.
When the photograph is developed, they realise that the woman's male companion is Emile Zubova (Franklin Dyall), a notorious illegal arms dealer who had recently been reported as having committed suicide while on the run from agents wishing to track him down.
Connelly and Garnett manage to identify the woman in the picture, Jacqueline Manet (Bouchier), and trace her movements to France.
Jacqueline arrives at the hideout and shoots Zubova during a struggle, but is herself fatally wounded in return and dies in Garnett's arms.
Garnett is able to alert the authorities of the plot to sink the liner, the navy are put on hand to deal with the threat, and the submarine is destroyed.