Sir Arthur Conan Doyle's most intriguing novella.

Austin Gilroy is a scientist and is by nature sceptical of anything to do with the occult. So when his colleague, Professor Wilson, introduces him to the mysterious and sinister hypnotist, Miss Penclosa, he is inclined to view her as a fraud.

But when Gilroy's fiancée is hypnotised and Miss Penclosa makes her do the unthinkable, Gilroy is forced to change his views. He embarks on a series of hypnosis experiments with himself as the subject this time... but it soon becomes apparent to him that the odious Miss Penclosa has fallen in love with him and is now manipulating him to her own ends. Her power over him seems absolute ... can he ever manage to extricate himself from her evil clutches?