Bartholomew is found dead in his home from a poison dart and the treasure is missing. While the police wrongly take Thaddeus in as a suspect, Holmes deduces that there are two persons involved in the murder: a one-legged man, Jonathan Small, as well as another "small" accomplice. He traces them to a boat landing where Small has hired a launch named the Aurora. With the help of his dog Toby and the Baker Street Irregulars and his own disguise, Holmes traces the launch. In a police launch Holmes and Watson chase the Aurora and capture it, but in the process end up killing the "small" companion after he attempts to kill Holmes with a poisoned dart shot from a blow-pipe. Small tries to escape but is captured. However, the iron treasure box is empty; Small claims to have dumped the treasure over the side during the chase.