Sheldon, a young Roman Snail, lives in an old man's walled garden where he is much loved and respected by the other small residents. In early spring he emerges from hibernation and starts to rediscover his surroundings, but on the garden grapevine he hears the local magpies, led by the fearsome Moriarty, had been on a raid, and stolen away the previous year's baby frogs. Only one has survived. In the garden pond, Poseidon, the old grandfather frog, is so depressed by the loss of his little ones that the various small creatures, including a large spider, newts, woodlice, bees and many others realise there has to be a plan to prevent this from ever happening again. And also to seek some revenge. They turn to Sheldon for his wisdom and masterminding. He forms a committee which includes the centipede with healing skills and Poseidon's grown up nephew, who has who has returned to the garden to offer support. Moriarty and the clan do reappear on a sultry August day but a surprise is in store, all masterminded by the intelligent young snail.