Dir. Morten Tyldum. Starring Benedict Cumberbatch, Keira Knightley, Allen Leech

The Imitation Game is structurally deficient. By virtually any standard it’s got all of the best elements of a good biopic: a well-known (but not too well-known) historical figure with some relevance to even casual viewers, a story which relates back to an important historical moment, a shoal of Oscarbait actors, casual and inoffensive direction.

(The Imitation Game is not particularly true to life, but to me that’s praiseworthy: if you want straight fact, then a movie is hardly the right place to learn. Something that The Imitation Game actually does very well is creating obviously false historical moments which create greater drama, or smooth the plot. The premise of much of the film – that you could fit all of serious cryptanalysts working on Enigma into a single room, even though British high command recognizes that cracking Enigma could win the war – is absurd. Then there are relatively smaller moments, like the way that Turing gets Churchill to make him the leader of the Enigma code-breaking project, or when Turing realizes, only with an arbitrary time limit staring him in the face, that certain words will be reused. My personal favorite occurs when the people at Bletchley Park make an executive decision about whether or not to inform a convoy in the Atlantic about a squadron of U-boats – how on earth would that have happened? But each of these decisions make sense from a storytelling perspective, and when the choice is “historical accuracy/textual fidelity” or “engaging, character-building narrative,” only a fool of a filmmaker prioritizes the former. The sooner we all recognize that directors, screenwriters, and actors don’t have obligation to historical truth, the better.)

The problem is, although The Imitation Game was clearly formulated as a biopic about the life of Alan Turing, the first two-thirds of the film, which primarily concern the Enigma code, badly outstrips the final third, which is primarily about Turing’s illegal homosexuality, in quality. The whole movie is about Turing, but the element that the filmmakers privilege, the ones which are supposed to have the greatest emotional effect on the viewer, have to do with Turing’s sexuality. We can tell because the film begins with a mystery: Who broke into Turing’s home, and why doesn’t he seem to care? A policeman named Nock (Rory Kinnear), who’s not so dumb but a little big for his britches, deduces that Turing’s seeming apathy about the break-in means he’s hiding something from the police. It’s the early ’50s! What if Turing is a Commie spy? Over the course of the film, Nock realizes that he was right, sort of. Turing was trying to hide something from the police, but it’s not as juicy as Nock had hoped; Turing was soliciting sex from a male prostitute and was trying to turn the cops off his scent. If not for the placement of this scene, the movie would be guilty of a lengthy denouement, which, when it’s done well, is no sin at all. But it comes at the beginning; whether or not the film means to do it (which it does, incidentally), that lays extra importance on Turing’s homosexuality as a plot element. Even if we grant that Turing’s latter-day status as a gay martyr outstrips his importance to Allied victory in World War II (which is not a slam-dunk answer in either direction), the film’s most engrossing elements don’t support its own thesis.

The Imitation Game can at times feel like a holiday special of Sherlock. Cumberbatch, for better or worse, will always be associated first with his take on Sherlock Holmes, which is as definitive for millennials of a certain ilk as Rathbone’s Sherlock is for people who can remember seeing Gone with the Wind in theaters. Turing via Cumberbatch is much the same: socially inept as ever, utterly focused on a task which will primarily require his brilliance to solve, possessed of enough accidentally sardonic one-liners to endear himself to the audience which doesn’t have to deal with him. Cumberbatch is surrounded by a host of second-level name-brand British actors, which he bounces off of for a little while. Mark Strong plays General Stuart Menzies of MI6 vis-a-vis his performance in the Jaguar ads that were airing about the same time the movie was being released. Charles Dance brings Tywin Lannister sans bloodlust to Bletchley Park, which is rather more welcome. His Commander Denniston is a worthy rival to Cumberbatch’s Turing; Denniston wants Enigma broken because he’s a patriot trying to win a war, and Turing wants Enigma broken because it’s a particularly marvelous puzzle. I’ve always liked Matthew Goode, and his performance as British chess champion and cryptanalyst Hugh Alexander mishmashes the most interesting elements of his characters in Match Point and A Single Man. Allen Leech, who appears to have masterminded a Downton Abbey jailbreak with Goode, plays John Cairncross. Leech’s character is the kindest of the Bletchley Park gang, and also the one sending English secrets to the Soviet Union. It’s something of an open secret; Turing figures it out (as Cairncross has figured out that Turing is gay), tells Menzies in a tense moment, and finds out that Menzies has known for a very long time, before Cairncross was ever placed at Bletchley Park. It’s a fairly clever device giving Turing a foil with a secret, one of the two links which can connect Turing’s codebreaking career with his homosexuality.

There are certainly a lot of men running around in this movie, which may be one of the reasons why Keira Knightley stands out as much as she does. Joan Clarke is the film’s most engaging character, and watching Knightley, one wonders why this isn’t her movie. The social aspect of the period drama could certainly have been maintained. Clarke’s mathematical brilliance, on the same plane as Turing’s in the film, is placed in opposition with her sex by virtually every person in the film. There’s a very good story about a woman who was old enough to understand the importance of universal women’s suffrage in the U.K. when it happened in 1928, who was all but shut out of the Enigma codebreaking team because of her sex, whose invaluable contributions would have been dust in the wind if not for the meritocratic eye of her gay boss, Alan Turing, who knows that straight white men have a long history of underestimating people they unjustly judge to be lesser quantities. That story is in The Imitation Game. Again, it’s not the focus – Clarke supports Turing’s story, not the opposite way round – and that’s too bad. Knightley, as she has quietly been often as not even since the first Pirates of the Caribbean, has a strong argument for being the best part of the movie.

Knightley has played acerbic and tough (Bend It Like Beckham, Never Let Me Go), and she’s been a human marshmallow (Love Actually), but those tend to play hollow. Real-life Knightley, as far as I can tell, doesn’t miss a trick. Her most interesting characters reflect that quality as well. Joan seems a little too sweet for stretches of the film, especially when we first run into her, but as it progresses it’s clear that there’s a genuine person under there. At one point late in the film, Turing tries to drive off his fiancee, believing that Joan’s involvement with the team at Bletchley Park will end in her arrest or something worse. He tells her that he’s gay. I haven’t seen a movie which addresses this relatively blase confession in the way that Joan does, and Knightley sells it in a scene which balances anger, compassion, and cool logic. Her answer boils down, essentially, to “Why should that matter? We care about each other, appreciate each other, and go well together.” Turing has an answer for many things, but he struggles to come up with a retort. And at the very end of the film, when Turing has long been chemically castrated, Knightley manages to emphasize those three emotions again to help Alan believe that his life has held more meaning than “state-punished homosexual.” It’s a role that got Knightley her first Oscar nod since Pride and Prejudice. (Right now, I would place it below Pride and Prejudice, Atonement, A Dangerous Method, and Anna Karenina as a whole – apologies to Curse of the Black Pearl.) At 31, one can reasonably imagine another forty years and more of Knightley performances. Even if this isn’t her best film, this is another step in expanding her reach; as in A Dangerous Method, the fact that Knightley is one of the world’s most beautiful women is totally unimportant to the character she’s playing.

As John Cairncross and Joan Clarke fade out of the film’s primary narrative, so too does the film fade. The scenes in which Turing’s machine, “Christopher” (named for a childhood friend who died very young), decode an Enigma message and the team decides not to warn a British convoy to change its route so as to maintain the illusion that Enigma is unbroken are perhaps the two best in the film. The qualities which made Turing interesting – his brilliance, his brusqueness, his first group of friends and collaborators – fall away in the service of a story which was not developed fully enough in the early going. Turing is gay, and is persecuted by his government, and, in the film’s telling, driven to suicide. This will sound dismissive, but it is in fact high praise: The Imitation Game would have made one heck of an HBO two-part miniseries. Devoting equal time to the two elements of Turing’s story would have been much more fair, and would have given viewers ample reason to care about Enigma as much as its equally mysterious conqueror.