Promising his mother he'll stay out of trouble, young Billy arrives on the resort island of Catalina to spend the summer with his father, an eccentric inventor and toy maker. But Billy's summer takes a turn toward astonishing adventure when he meets Sherlock, a talking dog who claims his policeman master has been kidnapped by smugglers! Since Sherlock only chooses to speak to Billy and his newfound friend Emma, it's up to the two kids and their canine sidekick to crack the case.