In present-day Jersey, Professor Alan Stacy John Standing arrives to finish a biography of his friend and pre-World War II scholar Harry Martineau, only to find himself at the funeral where the lone mourner is Dr. Sara Drayton Deborah Raffin. Invited back to her house, Sara reveals that the two of them worked for the Special Operations Executive during the war and shows Stacy a photo of them posing with Field Marshal Erwin Rommel, played by Michael York, before recounting the story behind the image.
The wartime flashback opens in the aftermath of the Slapton Sands disaster. Hugh Kelso David Birney, a US Army colonel, washes ashore on Jersey and is rescued by Hélène de Ville Andréa Ferréol, who then contacts London. Brigadier Dougal Munro, of the SOE, realizes Kelso carries critical knowledge about the planned D-Day landings and decides that Kelso must be either rescued or eliminated. He recruits Harry Martineau, a former academic who has become a ruthless operative, and Sara Drayton, whose cover is that of Anne-Marie de la Tour, a wealthy French mistress, to carry out one last mission. Harry, who has previously operated in Germany, assumes the identity SD Standartenführer Max Vogel, a role forged with a letter of authority signed by Hitler and Himmler. The two are smuggled to France and then to occupied Jersey, while Kelso remains on edge, aware of Harry’s fearsome reputation.
Harry sails on a naval vessel, but Sarah, traveling as a civilian, must ride a cargo boat commanded by Captain Guido Orsini Andrea Occhipinti. Kelso’s anxiety grows as he senses the danger in their rendezvous, since he knows the consequences of the mission. The plan to evacuate Kelso is disrupted when a surprise visit from Rommel occurs—though the truth is that the “Rommel” is Corporal Erich Berger, a German officer who has been acting as the field marshal’s double. The real Rommel has become involved in a plot to assassinate Hitler and needs to be away from Germany for the moment.
A crucial twist emerges when the operation is nearly derailed by a German military policeman; Berger is unmasked by Harry, who extracts permission to operate from Berger. Berger confesses that he is actually Heini Baum, a German Jew who has assumed the dead Berger’s identity and has survived the war. The mission’s fortunes swing back in their favor, but a Luftwaffe night fighter is dispatched to intercept them. The team fights to gain the upper hand, and one crew member is killed as they execute a high-stakes maneuver: Harry orders the plane to fly at almost sea level to draw the fighter away, causing the aircraft to crash near the coast.
With radio contact established to the RAF, they press on toward England. Landing earns them a tight, tense scrutiny from armed soldiers; Baum darts forward in a final act of bravery and is shot, seemingly by accident, though it’s implied that Munro may have ordered it. As he dies, Baum begs Harry to say Kaddish for him, a moment that underscores the personal costs of their covert work.
Back in the present, Sara reveals what happened after the war: she eventually married Orsini and lived in Florence as Contessa Orsini. Harry continued his SOE work but was shot down by friendly fire a few months later, and his body was buried in the Essex marshes—its location only recently discovered and given a belated, proper burial.
