Holmes and Dr. Watson find themselves at Poldhu in Cornwall one spring for the former's health, but the holiday ends with a bizarre event. Mr. Mortimer Tregennis, a local gentleman, and Mr. Roundhay, the local vicar, come to Holmes to report that Tregennis's two brothers have gone insane, and his sister has died. Tregennis had gone to visit them in their village ('Tredannick Wollas'), played whist with them, and then left. When he came back in the...