"It's bedtime for Amos, who smiles as he closes his eyes and counts some fluffy sheep trotting away in the grass. Until suddenly . . . THUD. And then another. “Not again!” says the first sheep, now on Amos's floor. “I was having my wool clipped,” grumbles the second. None too happy at being interrupted, the woolly pair fire a battery of questions at Amos, most importantly: "Where's the fence?" So Amos sets out to build one to their specifications,...