Benedict Cumberbatch stars in The Avengers for math nerds. As Alan Turing, he assembles a crack team called Hut 8 who will secretly try to break the unbreakable German code machine, Enigma, to win the war, while pretending to be regular schmos putting in time at a radio factory.

Turns out, pretending to be regular is probably the bigger of the challenges for Turing. He’s a genius, but he’s also probably autistic. He’s horrid with people, often laughably so in the film (Cumberbatch portrays him lovingly, with sensitivity, grace in his gracelessness, and touches of clueless humour). Turing is also gay, and closeted, necessarily. Churchill credited him with the single largest contribution by an individual to the war effort; his work probably shortened the second world war by at least two years. He was an expert in his field, the father of computer science, and a war hero and yet he struggled just to make a friend.

The film flips between different time periods: his boyhood at school where he had his first love, a post-war break-in of his home that leads to him being interrogated by police, and the time he spent at Bletchley Park deciphering Nazi codes. Both book-ending periods paint us, the audience, a picture of the things he’s keeping secret. The film does an excellent job of presenting his world as a series of codes: as a boy he confesses that for him, conversation is a code. People are an enigma. The wallpaper in his home looks like morse code, dashes and dots. The production design is upscale period all the way.

For a movie about math and cryptology, it’s surprisingly gripping. Reels of news footage help give us a sense  of their urgency. They aren’t battling Germans, they’re fighting a clock. Their countrymen are dying in tunnels during air raids (as Keira Knightley already did, in Atonement), or simply wasting away of starvation. The movie isn’t 100% historically accurate, but I think it’s faithful to the time and place and people, and if the computer itself is given the Hollywood treatment, looking much more impressive than it ever did in real life, where’s the harm? Perhaps it will inspire people to go home and look it up.

I think the film’s strength is its moral question. Once the code is cracked, how and when can that information be used? How many civilialns and soldiers would you sacrifice to keep a secret that could win the war? The movie does a great job of personalizing the question and we start to feel that as awful and tense as it was in the not knowing, it was a lot more bearable than the responsibility we’re faced with when we do know. The weakness is in having painted Turing as the unblemished hero. The truth is , he was probably unknowable, and without ever having known him, I’m betting that no one could be as spotless as he’s implied to be in the film. Turing, the actual man, was mistreated by his ungrateful government, who kept his war records sealed while he was prosecuted for simply being a gay man at a time when it was illegal to be so (or at least to act on it – “gross indecency” they called it, hypocritically), and then sentenced him to chemical castration, robbing a nation, and the world, of a great mind.