Sherlock Season 4: 20 Easter Eggs & References From The Six Thatchers

17. The Canary Trainer

Speaking of DI Hopkins, the case Sherlock is helping her solve is called The Canary Trainer on John's blog. Naturally this is a reference to a pre-existing Sherlock Holmes story. Unusually, though, it is not one of Conan Doyle's.

The Canary Trainer is actually a novel by Nicholas Meyer, whose most famous work of Holmesian fiction is The Seven Per-Cent Solution, which controversially depicts Holmes as having delusional tendencies.

Geeks will most know Meyer as the writer/director of seminal Star Trek movie The Wrath of Khan (as well as penning The Undiscovered Country).