Old Dog New Tricks

Holly was just getting settled in at Happy Hollow Stables when she found herself being adopted by a German shepherd that showed up looking for food. 

Since the dog arrived without a collar or any type of identification, she took him to the local vet to help search for his owner.  The vet checked him for a microchip, but couldn't find anything.  Since she was unable to locate his owner, Holly decided Happy Hollow Stables could be his new home away from home until his owner could be found.

Soon after the dog got familiar with his new surroundings, Holly discovered he seemed to have yet another secret.  How will she find out what it is?