What is the title of the final regular episode of BBC’s Sherlock?

“The Final Problem” is the final regular episode of BBC’s Sherlock.

It is the third episode of series 4 and was first broadcast in January 2017. The story centres on Eurus Holmes, Sherlock and Mycroft’s highly intelligent sister, and takes place largely around a dangerous series of psychological tests.

The title echoes Arthur Conan Doyle’s “The Final Problem,” the story associated with Sherlock Holmes’s confrontation with Professor Moriarty. The television episode expands that idea into a family mystery involving childhood memories, isolation and the Holmes siblings’ past.

It is sometimes mistaken for “The Reichenbach Fall,” which is the third and final episode of series 2, or “His Last Vow,” the third episode of series 3. “The Final Problem” is the last regular episode released in the programme’s four-series run.