On holiday at her uncle's farm in New Zealand, Gretchen befriends Ronny, a Māori boy with a troubled city past, and Bevis the birdwatching son of a loathed developer. Tension is high as the developer wants to buy and drain the local swamp for a housing estate. Local legend talks of a curse and the swamp must not be touched as something sleeps there that must not be awakened. Something unnatural.

    Gradually, the children discover the pieces of an ancient alien space probe named. The probe was one of three sent to earth to educate the human race in science. In the end a communication link is set up with the star Sirius B, from where the probe came, and the aliens tell them they should not have interfered.