A level 4 Oxford Bookworms Library graded reader. Retold for Learners of English by Peter Hawkins.
If you find a locked room in a lonely inn, don't try to open it, even on a bright sunny day. If you find a strange whistle hidden among the stones of an old church, don't blow it. If a mysterious man gives you a piece of paper with strange writing on it, give it back to him at once. And if you call a dead man from his grave, don't expect to sleep peacefully ever again.