Castle Sinister

During WWII, Major Matthews is pushed from a cliff at Castle Glenye by a masked Phantom. The assault abruptly ends the counter-intelligence operation and sets a tense mystery in motion. The attacker vanishes into the Scottish Highlands, leaving questions behind.

Shortly after Matthews' fall, Captain Fairfax vanishes without a trace on the Glenye estate. The missing officer hints at a wider conspiracy lurking within the castle's walls. The loss deepens the sense that something dangerous is at work.

The War Office sends Captain Neale to uncover the truth behind the disappearances and the Phantom sightings. He arrives to gather evidence and question those connected to Castle Glenye. His presence signals that the mystery has national security implications.

In a flashback, the Marquess dies leaving Lady Glenye with two sons, Michael and Nigel. Nigel is jealous of Michael's standing as laird, while Michael is a conscientious objector. The Phantom rumor begins to take hold amid the castle's mounting intrigues.

Nigel returns on leave as a captain and breaks his leg in a riding accident. Jean Hamilton nurses him, but his recovery drags on for six months, preventing a full return to combat. The extended layoff fuels Nigel's secret plans and dependence on the castle's routines.

Lord Glenye's rifle is discovered missing, and the missing Captain Fairfax is found shot dead on the estate. The discovery deepens the sense of danger surrounding the Glenye household. Investigators begin connecting the dots between personal vendettas and strategic secrets.

Searchers report seeing the Phantom, and the figure is even encountered by the cook and the local constable. The specter becomes a tangible symbol of the conspiracy at Castle Glenye. Fear and superstition mingle with the political intrigue.

Major Selwyn, Nigel's physician, arrives at the castle, and Lady Glenye immediately recognizes him. His presence adds a chilling medical authority to the suspicions swirling around Nigel. The tension tightens as loyalties and motives blur.

The Phantom attacks the chauffeur and ties up the housekeeper, escalating the danger around the castle. Lady Glenye confronts the Phantom but is captured, revealing the depth of the conspiracy. It is soon revealed that the Phantom is Nigel, aided by Selwyn as Baron Karl von Reiten.

It is revealed that the Phantom is Nigel and that Selwyn is Baron Karl von Reiten, Nigel's father. Nigel has been feigning a still-injured leg to hide from war and to assist Selwyn in obtaining secret military plans. The deception ties Nigel directly to the attempted espionage.

Jean Hamilton watches from the wings and goes to fetch help as the danger nears a critical moment. Selwyn responds by signaling an incoming German aircraft, signaling that the spy operation is close to exposure. The castle gears up for a confrontation with far-reaching consequences.

Nigel rebels and throws the secret plans into the fire, attempting to destroy crucial information. Selwyn shoots Nigel, and Michael and McWerter arrive to pursue Selwyn. The pursuit ends with Nigel mortally wounding Selwyn, who falls from a cliff to his death.

Michael tries to conceal Nigel's involvement from Captain Neale, but Neale suspects that Selwyn had an accomplice. The web of deception tightens as the truth edges closer to daylight. The investigation begins to salvage the truth from a web of lies.

Michael reveals that he works for British Intelligence, choosing to protect the Glenye family by downplaying Nigel's Nazi sympathies. He states Nigel was undercover, wearing the Phantom costume to spy on Selwyn. Neale tells Lady Glenye to be proud of both her sons as the truth comes to light.