What curious episode occurs in the study?

Explanation

A clergyman and his wife were awakened by noises in the study very early in the morning. Creeping downstairs, they heard the chink of money being taken from the clergyman’s desk. He and his wife looked under the desk and behind the curtains, and even up the chimney. There wasn’t a sign of anybody. Yet the desk had been opened and the housekeeping money was missing.