Margaret Lockwood is a scientist ("Frances Gray") who is asked by the British government to travel to the Balkans to discovers whether the communists there are trying to weaponise the humble fruit fly! Initially nervous, she takes courage from a radio serial that she listens to for her young nephew, and is soon embroiled in some espionage shenanigans with American journalist "Casey" (Dane Clark) as they try to get hold of one of these critters to return to the UK for evaluation. Local commandant "Razinski" (Marius Goring) cottons on quite quickly that something is afoot, but can the two comple...