The newly married Elizabeth arrives with her new husband, the scientist Henry, at a magnificent house. He tells her that she can do there anything she pleases, except to enter a certain closed room.

Based on the real life story of legendary cryptanalyst Alan Turing, the film portrays the nail-biting race against time by Turing and his brilliant team of code-breakers at Britain's top-secret Government Code and Cypher School at Bletchley Park, during the darkest days of World War II.