A specialist in nervous maladies and catalepsy who seeks Holmes’s help after his practice is "intruded" upon.

The consulting detective who unmasks the deception behind a staged suicide.

The narrative follows Dr. Percy Trevelyan, a talented but penniless physician who enters into a singular business arrangement with a mysterious benefactor named Mr. Blessington. Blessington funds a prestigious practice for Trevelyan in exchange for a large share of the profits and a room in the house as a "resident patient". The case shifts from a medical curiosity to a capital crime when Blessington is found dead under suspicious circumstances, eventually revealed by Holmes as a calculated act of revenge.

Two men posing as a Russian Count (suffering from catalepsy) and his son visit the doctor. While the son "waits," he explores Blessington’s private rooms upstairs.