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 . . .