On a secret island, three aunts, Etta, Coral and Myrtle, kidnap three children from London to help with such tasks as cleaning mermaids who were caught in an oil slick. Two of the children, Fabio and Minette, grow to love the island and its inhabitants, but the third, Lambert, nearly ruins the island when he is rescued by his father, who attempts to exploit the island's creatures for his own gain.

Published by Penguin as: Island of the aunts. Published by Macmillan as: Monster mission. Includes preview of Mountwood School for ghosts, The Beasts of Clawstone Castle, The secret of Platform13, Which witch?