Swedish director Tomas Alfredson (Let the Right One In) purposely makes you work. His adaptation of John le Carré’s 1974 seminal spy saga immerses you in East vs. West spy games—you either sink or swim. By osmosis, you’ll become an active player, forced to keep the spider web plot in your head. Don’t count on any bathroom breaks or you’ll be lost.

Alfredson takes the intelligence of the viewer seriously, and renders le Carré’s novel beautifully, shot mostly in brown and greyish earth tones evoking early 1970s Britain. The overall production design lives up to one of the film’s observations that “The West has become so very ugly.” But can the film shake off the spook of the classic BBC miniseries made in 1979, with Alec Guinness as spy George Smiley? In its own fashion, yes. It doesn’t have the luxury of nearly six hours for le Carré’s weighty narrative. However, the momentum keeps at pace with the unfolding and tangled subplots. Even within a compact and complex two hours, the mystery at the heart of the film still weaves a spell.

Smiley (now Gary Oldman) pulls himself out of retirement to track down a double agent within the highest level of British intelligence planted by the Russians. He had been warned by his boss Control (John Hurt) that someone in MI6 (aka “the circus,” don’t worry, you’ll pick up the lingo) has been leaking information to the enemy.

The cast, the most illustrious British ensemble to appear outside of a Harry Potter film, has a discreet confidence. It’s a director’s dream, featuring Colin Firth, John Hurt, Mark Strong, and Tom Hardy, who, as a renegade British agent involved in a doomed romantic liaison with a Russian, is just a film away from becoming a star. As Smiley’s sole female colleague in this club of male bravado, Kathy Burke appears as researcher Connie (“I don’t know about you George, but I feel seriously under fucked”) Sachs.

Oldman plays the impeccably mild mannered Smiley (he still wears his spectacles even while swimming) with an extra spring in his step. Smiley’s an observer, careful not to reveal too much. As he pieces together the clues leading to the traitor, flashes of something like hunger pierce through the thick lenses of his large framed glasses. (You never forget that you’re stuck in the ’70s; even the title sequence has the sparseness of All the Presidents Men.) And you will swear at times his voice has a resonance just like Guinness. But it’s also a quiet performance, one that will probably get lost in this year’s awards season hype. Oldman personifies the definition of “measured.”

The script packs in a lot, sometimes moving forward before you absorb the latest bombshell. There’s not always enough time for the characters or the plot twists to breathe. Like the adaptation of le Carré’s The Constant Gardner, the running time of a feature-length film limits the author’s expansive and serpentine storyline. But by intercutting sequences, set in London and Istanbul for instance, Alfredson keeps the film spiraling along—the cold war is hot again. The film begs for a second viewing just for clarity, and you will want to see it again anyway. Even then it leaves much to the imagination—you’ll have a new list of questions to decipher.