Detective Sherlock Holmes and Dr. John Watson join forces to investigate a murder at Buckingham Palace. They soon learn that they have only four days to solve the case, or the queen will become the next victim.

The film is based on the story of William of Cambridge and Catherine Middleton. Shown in the same life of William of Cambridge, and Catherine Middleton met at the University of Saint Andrews, besides the romance that they maintained, the break of it and commitment.