Twins Georgia and Adam can't wait to go on their holiday to Cornwall - especially as it's the first time they're taking their new puppy, Lucky, with them. Lucky loves the seaside - chasing the waves, digging in the sand and the long cliff-top walks. One day, the children go out by themselves, but they get into difficulty and the puppy ends up falling partway down a cliff. Unable to reach him themselves, the twins are distraught to see Lucky's paw is hurt, too. Will they find a way to rescue poor Lucky?