It's 1943 and Claus von Stauffenberg (TOM CRUISE) is a colonel in the German army who's been badly wounded in Tunisia. While proud to serve his country, he's come to dislike what Adolf Hitler (DAVID BAMBER), the Nazi party and the SS have come to stand for, as well as their actions. Accordingly, he's drawn the attention of Major-Gen. Henning von Tresckow (KENNETH BRANAGH) who's been leading the underground resistance movement against the fuehrer and even attempted but failed to assassinate him, barely avoiding being connected to one of many such plots. Undeterred, he and war hero Gen. Friedrich Olbricht (BILL NIGHY) recruit von Stauffenberg in hopes that he'll help them modify Operation Valkyrie, Hitler's plan to have a reserve army, overseen by Gen. Friedrich Fromm (TOM WILKINSON) and directly controlled by Maj. Otto Ernst Remer (THOMAS KRETSCHMANN), at the ready.
After sending off his wife, Nina (CARICE VAN HOUTEN), and their children to safety, von Stauffenberg and his personal assistant, Lt. Werner von Haeften (JAMIE PARKER), along with the assistance of retired Gen. Ludwig Beck (TERENCE STAMP), resistance leader Dr. Carl Goerdeler (KEVIN R. McNALLY) and Col. Mertz von Quirnheim (CHRISTIAN BERKEL), among many others, attempt to rewrite Valkyrie's operational status in 1944. Their goal is to make it appear as if the SS has assassinated Hitler and thus turned enemy of the state, and then use his reserve army to take out the SS.
Of course, that means they have to kill Hitler first, and with the aide of Gen. Erich Fellgiebel (EDDIE IZZARD), von Stauffenberg and von Haeften manage to make it into the "Wolf's Lair," hoping to get close enough to the supreme commander in order to set their assassination and coup plot into motion.