The Griffin's Riddle (The Imaginary Veterinary Series #5)

A mysterious sickness from the Imaginary World is sweeping the town of Buttonville. Dr. Woo, Metalmouth, and even the sasquatch have fallen ill. According to Mr. Tabby, the only known cure is a griffin's feather, but there is none in the hospital.
Keeping an eye out for Maximus Steele, a poacher wanted for crimes against Imaginary creatures, Ben, Pearl, and Mr. Tabby make their way through the Portal. But danger looms on the other side. Can they persuade the griffin, king of the Imaginary Wor…