Inspector Lestrade arrives at Baskerville Hall to help the detectives. In the evening, the three organize surveillance near the Stapleton house. Watson sees that Jack Stapleton has already released the dog - a huge Great Dane with a muzzle smeared with phosphorus - just before Sir Henry left. The dog attacks Henry and almost bites him to death, but Lestrade kills the dog with several shots. Stapleton, however, hides. The detectives search his house, find a tied-up Beryl and bring her to consciousness. The woman says that Jack can only hide in the center of the Grimpen Mire, where he kept the dog. There, Holmes finds all the evidence: Sir Henry's boot stolen to set the dog on, the remains of Dr. Mortimer's dog Snoopy, and phosphorus. A shot is heard, and a shootout with Stapleton begins. Escaping from pursuit, Stapleton drowns in the mire.
