The Signal-Man

"Halloa! Below there!"
Unable to sleep one cold winter's night, a gentleman wanders aimlessly around the countryside and comes across the dark mouth of a railway tunnel. There he spots an old signal-man, but when he calls out to him the old man is unresponsive. Managing to convince the signal-man that he means no harm, the old man invites him to his small, lonely shack. There, the gentleman learns a horrifying secret. But how well can he really trust the old Signal-Man?
The Signal-Man is a masterful ghost story which has been adapted for TV and radio several times. In a Doctor Who episode from 2005 called The Unquiet Dead, the Doctor, played by Christopher Eccleston, called it "The best short story ever written."