Cottage to Let

John Barrington, a talented but eccentric inventor, is hard at work on a new bombsight for the RAF at his Scottish country home. His scatter-brained wife agrees to take in London evacuees, but they decide to shelter only one, a cocky teenager named Ronald. The arrangement foreshadows the clash between secrecy and ordinary family life that drives the story.

An injured pilot parachutes into a nearby loch and is rescued, then brought back to the house. The cottage becomes a partial hospital with Barrington's daughter Helen acting as nurse. The pilot identifies himself as Flight Lieutenant Perry, linking the domestic drama to the war's broader operations.

While Perry is given a telephone to contact his headquarters, he makes the call himself and fails to connect properly because the phone wire is disconnected. The suspicious interruption hints at covert interference and raises questions about the security of Barrington's secrecy. The incident deepens the sense that someone is spying on Barrington's work.

At the War Office, officials discuss Barrington and fear a security breach around his top-secret research. They suspect his German-educated assistant, Alan Trently, who still maintains covert contacts in Switzerland. A formal investigation is ordered to uncover any espionage within Barrington's circle.

Ronald breaches house rules by wandering into Barrington's laboratory, where his practical know-how earns Barrington's grudging respect. The pair form an unlikely alliance as they collaborate on a problem related to the bombsight project. Their budding friendship anchors the human side of the espionage tale.

Trently grows jealous as Helen spends time with Perry, complicating loyalties in the household. Helen resists the pilot's advances and ultimately tells Trently that she prefers him. The personal tensions add a human stake to the espionage plot.

One evening Barrington is kidnapped by German agents, who take him away in a car. Ronald stows away in the car's boot to follow them, determined to help. The captors deposit both Barrington and the boy at an isolated, off-road water mill where the stakes escalate.

Ronald sneaks into the mill and watches as Perry arrives in a second car. He is shocked to learn that Perry is a German intelligence agent intending to fly Barrington to Berlin by seaplane. The discovery confirms that the mission is a coordinated espionage operation tied to a wider spy ring.

Dimble is revealed to be a British counter-intelligence officer, quietly infiltrating Perry's spy ring. He identifies Barrington's location and orchestrates a plan to rescue him. The operation shifts from domestic intrigue to a coordinated security raid.

All but one of the spies are captured and Barrington and Ronald are freed. Dimble's team seals the operation, neutralizing the immediate threat to Barrington's work. The rescue marks a turning point in protecting the scientist and his secrets.

Perry initially escapes but is tracked down in a final pursuit and killed in a shoot-out with Dimble. The German intelligence operation is thwarted, and the spy network loses its key asset. Barrington's secrecy remains intact as the war effort continues.

With the spy ring dismantled, Barrington's research remains secure and the War Office's concerns are allayed. Dimble continues his counter- intelligence work, overseeing ongoing security. The cottage-turned-hospital operation returns to normal life, though the memory of the raid lingers in the household.