Although the story is highly fictionalised, the process of encrypting German messages during World War II and decrypting them with the Enigma is discussed in detail, and the historical event of the Katyn massacre is highlighted.

The cryptanalysts at Bletchley Park, Buckinghamshire, have a problem: the Nazi U-boats have changed one of their code reference books used for Enigma machine ciphers, leading to a blackout in the flow of vital naval signals intelligence.

The film begins with Tom Jericho returning to Bletchley after a month of recovering from a nervous breakdown brought on by his failed love affair with a coworker named Claire Romilly.

The film holds a 'fresh' 72% rating on review aggregator Rotten Tomatoes, with the consensus reading, "The well-crafted, twist-filled Enigma is a thinking person's spy thriller.

"[6] Joe Leydon of Variety compared the film to works by Alfred Hitchcock, and remarked that, 'Overall, "Enigma" plays fair and square while generating suspense with its twisty plot.

And while it requires a generous suspension of disbelief to accept a few action-hero gestures by the deeply troubled Jericho, Scott is persuasive and compelling enough as his complex character to drive the narrative.

'[8] On the other end, Owen Gleiberman of Entertainment Weekly was far less impressed, saying, 'The legend of how the British cracked the almighty Enigma must have sounded, on paper, like a nifty mathematical thriller—a historic WarGames set at the formative moment of the computer age.

On-screen, however, Enigma plays as if the scriptwriter, Tom Stoppard, and the director, Michael Apted, were themselves cryptographers; they seem to be making hunt-and-peck stabs at how to translate a tale of arcane numeric formulas into drama.

[12] The film hints that Dougray Scott's character, the brilliant Cambridge mathematician Thomas Jericho is the main code-breaker at Bletchley, equating him with Alan Turing, the original creator of the British Bombe, with the words of Mr Wigram, played by Jeremy Northam: "But what if someone tells them just how we do it?

In the film, Cave, from Naval Intelligence, played by Matthew Macfadyen, mentioned Fasson and Grazier gave their lives to rescue the code books from a sinking submarine.

Fasson and Grazier did drown while attempting to retrieve electrical equipment from a U-boat U-559 (which Cave describes as its four-rotor enigma) on 30 October 1942, while Brown survived only to die in a house fire during shore-leave before the end of the war.