Private eye Slim Callaghan is summoned to the country home of a Colonel Stenhurst, but the latter is murdered before he can talk to the detective. Was one of the Colonel's three daughters responsible?

When a neutral Danish merchant ship is forced to put into port after trying to evade British wartime contraband control, its captain becomes involved in a beautiful British Naval Intelligent agent's efforts to capture a group of German spies operating from a London cinema.