The Adventure of the Beryl Coronet (The Adventures of Sherlock Holmes, Episode 11)

A banker asks Holmes to investigate after a 'Beryl Coronet' entrusted to him is damaged at his home. Awakened by noise, he had found his son, Arthur, holding the damaged coronet. Arthur refuses to speak, neither admitting guilt nor explaining himself. Footprints in the snow outside the house tell Holmes that the banker's niece had conspired with a blackguard to steal the coronet; Arthur had discovered the crime in progress and the coronet had been damaged during his struggle to prevent it being stolen. He had refused to tell his father the truth of the crime because of his love for his cousin.