Who Broke the Kangaroo's Hand?

Overview

During a training session to get the championship belt, the Kangaroo breaks his hand on the punching bag filled with horseshoes. Sherlock and Hermione investigate. Who is the culprit? The Old Horse, the Gorilla or the Chihuahua? Meanwhile, Hermione has kindly given Sherlock a car. But the detective doesn't dare tell her he doesn't have his driving permit.