During
World War II,
Wehrmacht Colonel
Claus von Stauffenberg (Cruise) is severely wounded in
Tunisia, and is evacuated home to
Nazi Germany. Meanwhile, Major General
Henning von Tresckow (Branagh) attempts to assassinate
Adolf Hitler by smuggling a bomb aboard the Führer's private airplane. The bomb, however, fails to detonate and Tresckow safely retrieves it to conceal his intentions. After learning that the
Gestapo has arrested Major
Hans Oster, he orders General
Olbricht (Nighy) to find a replacement. After recruiting von Stauffenberg into the
German Resistance, Olbricht delivers von Stauffenberg to a meeting of the secret committee which has coordinated previous attempts on Hitler's life. The members include General
Ludwig Beck (Stamp), Dr.
Carl Goerdeler (McNally), and
Erwin von Witzleben (Schofield). The Colonel is stunned to learn that no plans exist for after Hitler's assassination.
After a bombing raid on Berlin, he lights upon using the plan
Operation Valkyrie, which involves the deployment of the Reserve Army to maintain order in the event of a national emergency. The plotters carefully redraft the plan so that they can dismantle the Nazi regime after assassinating Hitler. Realizing that only General
Fromm (Wilkinson), the head of the Reserve Army, can initiate Valkyrie, they offer him a position as head of the Wehrmacht in a Post-Nazi Germany and recruit him into the fold. With the rewritten plan needing to be signed off by
Hitler (Bamber), von Stauffenberg visits the Führer at his
Berghof estate in
Bavaria. In the presence of his inner circle, Hitler praises von Stauffenberg's heroism in
North Africa and signs off on the plan without fully examining the modifications.
At Goerdeler's insistence, von Stauffenberg is ordered to assassinate both Hitler and SS head
Himmler at the bunker
Wolf's Lair. At a final briefing, Colonel
Mertz von Quirnheim (Berkel) instructs the committee members in how to use
pencil detonators. von Stauffenberg also reaches out to General
Fellgiebel (Izzard), who controls all communications at Wolf's Lair, to cut off communications after the bomb blast. On July 15, 1944, von Stauffenberg attends a strategy meeting at Wolf's Lair with the bomb in his briefcase, but with Himmler not present at the meeting, von Stauffenberg does not get the go-ahead from the committee leaders until the meeting is over. Meanwhile, the Reserve Army is mobilized by Olbricht, unbeknownst to Fromm, to stand by. With no action taken, von Stauffenberg safely extracts himself and the bomb from the bunker, and the Reserve Army is ordered to stand down, believing that the mobilization was training. Enraged, von Stauffenberg goes to the committee to protest the indecisiveness and blames the bungling of Goerdeler, who has been selected to be chancellor after the
coup. When Goerdeler demands that von Stauffenberg be relieved, Beck informs him that the SS is searching for him and implores him to leave the country immediately.
On July 20, 1944, von Stauffenberg and his adjutant Lieutenant
Haeften (Parker) return to the Wolf's Lair. To von Stauffenberg's dismay, he discovers that the conference is being held in an open-window summer barrack, whereas the plotters had intended to detonate the bomb within the walls of the bunker for maximum damage. While his adjuntant waits with a getaway car, von Stauffenberg leaves the briefcase at the meeting. With the bomb armed, von Stauffenberg leaves the barrack for the getaway car. When the bomb explodes, von Stauffenberg is certain that Hitler is dead and flees the Wolf's Lair. Before shutting down communications, Fellgiebel calls Mertz about the explosion but cannot clearly convey whether or not the Führer is dead.
As von Stauffenberg flies back to Berlin, Olbricht refuses to mobilize the Reserve Army until he knows without a doubt that Hitler is dead. Behind Olbricht's back, Mertz forges his signature and issues the orders anyway. With Operation Valkyrie underway, von Stauffenberg and his fellow plotters order the arrest of Nazi party leaders and SS officers and begin to take control of Berlin's government quarter, which will allow them to command the entire Reich. Rumors reach Berlin that Hitler survived the blast, but von Stauffenberg dismisses them as SS propaganda. Meanwhile, Fromm learns from Field Marshal
Keitel that Hitler is still alive. The General refuses to join the plotters, resulting in his arrest. When Hitler reaches the Reserve Army by telephone, the SS officers are released and the plotters in turn are besieged inside the
Bendlerblock. The headquarters staff flees, but the ringleaders are arrested. Most are eventually tried and executed, while some commit suicide. Von Stauffenberg shouts "Long live sacred Germany!" before being
executed by a firing squad.