A while has passed since Orinthia Shalloo's transatlantic adventure with her two younger brothers, and the Mailbox Menagerie is thriving, with trained animails delivering post. Then the Ambroses, a family of ice-cream makers, arrive in Little Penhallow, and announce that they're entering their ice-cream into the prestigious Golden Udder Awards in Norway. Orinthia and Dotty Ambrose decide to train a pair of cows to deliver a true show-stopper during the competition. But on the voyage to Norway and beyond, it's clear someone is determined to sabotage their efforts . . .