The Spy in Black

In March 1917, Captain Hardt is ordered to spy on the British Fleet at Scapa Flow. He rendezvouses with contacts near the Old Man of Hoy before sneaking ashore on the Orkney Islands. The mission is to observe fleet movements and identify a target for a German strike.

Hardt sneaks ashore on the Orkney Islands to meet Fräulein Tiel. Tiel has taken over the identity of a local schoolteacher, Miss Anne Burnett, to blend in with the islanders. Hardt is drawn to her, but Tiel shows little warmth.

A disgraced Royal Navy officer, formerly Commander Ashington, agrees to aid the Germans. Tiel implies she has slept with Ashington to secure his cooperation. Their arrangement makes the operation look like a routine local contact rather than a spy ring.

Burnett's fiancé, Rev. Harris, arrives unexpectedly and is captured by the Germans. A meddling local minister and his wife are deftly deflected away to avoid suspicion. The intrusion tests the operatives' cover and heightens the island's tension.

Hardt, armed with crucial information about British fleet movements, returns to his submarine to coordinate an attack. He plans to deploy a fleet of U-boats to strike a sortie of two Royal Navy squadrons. The success hinges on keeping the deception hidden from the British.

Back at the house, Hardt makes a romantic overture to Tiel, but she rebuffs him and asserts control over the mission. She slips out, believing she has locked him in, while Hardt secretly follows to learn her movements. He discovers she is leaving to meet Ashington.

Hardt overhears Tiel and Ashington plotting and realizes they are imposters. The British have turned his mission into a trap. Ashington is revealed to be RN Commander Blacklock, and Fräulein Tiel is his wife, Jill.

Jill prepares to depart the island while Blacklock returns to arrest Hardt. Hardt escapes by disguising himself in Rev. Harris's clothes and boards the island ferry, which carries Jill, civilian passengers, and eight German POWs. A tense pursuit begins as the escape becomes public knowledge.

Back at the base, Blacklock reports Hardt's escape to the commander. The base explains that the British had learned of the German plan when the real Anne Burnett briefly survived a failed attempt on her life.

At sea, Hardt frees the German prisoners and they seize the ferry. The Royal Navy pursues, but the ferry is intercepted by Hardt's submarine. Lieutenant Schuster orders the submarine to shell the ferry, creating chaos aboard.

Hardt realizes the shells are fired by his own submarine when it surfaces to engage. He frantically tries to signal his crew, but the moment escapes him. British ships arrive shortly after and begin depth-charge operations against the fleeing U-boat.

Jill and the remaining passengers manage to abandon ship in lifeboats as the ferry sinks. Hardt accepts that all is lost and chooses to go down with the ship, staying with his crew to the end.