The idea of Tom Cruise wearing an eye patch and a Nazi costume sounds like someone's idea of a bad Halloween party joke. But one of the many surprises of the new thriller "Valkyrie" is that it allows the actor, whose off-screen persona tends to overshadow his on-screen efforts, to disappear a bit inside the kind of old-fashioned theatrical get-up that Laurence Olivier might have exploited to the hilt.

Cruise doesn't quite have the gravitas to pull off this very tricky part - a German officer during World War II who leads a plot to overthrow Hitler - but he also doesn't try to hog the spotlight or oversell the audience on his charm, the way he has in a number of recent efforts, like "Tropic Thunder" and "Lions for Lambs." He blends into an excellently cast ensemble; and he modulates his performance to the tense, low-boil rhythms of the storytelling.

The actor plays Col. Claus von Stauffenberg, a real-life figure who was maimed and partly blinded in Tunisia in 1943. Upon his return to Germany, his disillusionment with Nazism became so pronounced that he joined forces with a number of members of the underground resistance - played here by the likes of Bill Nighy, Kenneth Branagh and Terence Stamp - to fashion an elaborate plot that will use Hitler's reserve army to turn against the rest of the army and take control of Berlin.

The only wrinkle: In order for the plot to succeed, Hitler must be assassinated.

For its first 45 minutes, "Valkyrie" (the title refers to Hitler's contingency plan in the event of a coup - a plan that Stauffenberg and company try to manipulate to their own benefit) is a bit of slog. Screenwriters Christopher McQuarrie and Nathan Alexander introduce the major players and try to keep us abreast of everyone's shifting alliances. (Tom Wilkinson and Eddie Izzard play generals who alternately support the conspiracists and betray them.) But unless you have an advanced degree in European history, you're likely to find yourself a bit lost.

Stick with it. Because even if you never fully understand everything that's going on in "Valkyrie," the movie reveals itself to be a taut, gripping procedural - not to mention a strangely poignant portrait of a madly quixotic group of men who refuse to go down without a fight.

Director Bryan Singer (who also collaborated with McQuarrie on "The Usual Suspects") takes an unfussy, just-the-facts-ma'am approach - so that when his familiar stylistic flourishes do occasionally emerge, they take your breath away. (Watch out for a stunningly beautiful shot of an out-of-focus Carice van Houten, who plays Stauffenberg's wife, running back into focus in order to kiss her husband goodbye.) The last section of the film is mesmerizing, especially if you don't already know the real-life history of the coup attempt (and provided you don't mind the filmmakers stretching the truth a little for the sake of good melodrama).

And while Cruise never fully captures what makes his tortured character tick, the movie ultimately functions as an intriguing metaphor for the star's place in the Hollywood cosmos: Stauffenberg - much like the actor playing him - is a man so used to being in control of things that, when all starts to fall apart and his acolytes begin to turn against him, he takes it as a personal affront. He keeps on fighting, too, determined to reclaim his place at the top, even as all evidence would suggest that his future is doomed.

In the end, Cruise's presence helps transform this history lesson into a very unique cautionary tale: It's the tragedy of a man whose hubris was inextricable from his glory.