Aviva miniaturizes Chris and Martin for an underground mission with earthworms, in search of the answer to the mystery "Why do worms come above ground when it rains?" But they have to hurry, as they soon discover that life as a worm is full of dangers at every turn. Science Concept: Wet objects can be changed by heating and cooling. If a worm is left in the hot sun, their skin will dry up and they will die. Worms need to stay wet and their environment helps keep them that way.