Sherlock Holmes is gravely ill and refuses medical treatment from his friend and colleague Dr. Watson. Holmes claims to have contracted a rare and deadly disease from his work on a recent case in Sumatra. He insists that Watson keep his distance to avoid becoming infected. Watson is skeptical of Holmes's story and demands to examine him, but Holmes refuses, claiming Watson lacks experience with tropical diseases. Holmes agrees to allow Watson to summon another doctor to examine him in two hours. As they wait, Holmes falls asleep while Watson keeps watch at his bedside, growing drowsy himself in the dimming light of evening.