The Strange Case of Dr Jekyll and Mr Hyde

The Strange Case of Doctor Jekyll and Mister Hyde was a novel by Robert Louis Stevenson.

In 1828, Doctor Robert Knox alluded to the novel during a conversation with Evelyn Smythe. Given that Stevenson would not be born until the 1850s, the Sixth Doctor realised that he mentioned the novel as a test for Evelyn whom he correctly believed may be another time traveller. (AUDIO: Medicinal Purposes)