Ronald Adair, a quiet young man whose only hobby was playing cards, got killed. Watson attempted to crack the case but with no success. One day he decided to examine the area around the victim's house and then he ran into a strange old man.
Who is he? Can it be the murderer who came back to the crime scene in disguise? Or the old man is simply a witness? Will Watson find out what happened by applying Holmes' methods or this will not be enough?
You can find the answers in "The Adventure of the Empty House" which is a part of "The Return of Sherlock Holmes".