Arthur (Art) Mumby and his irritating sister Myrtle live with their father in the huge and rambling house, Larklight, travelling through space on a remote orbit far beyond the Moon. One ordinary sort of morning they receive a correspondence informing them that a gentleman is on his way to visit, a Mr Webster. Visitors to Larklight are rare if not unique, and a frenzy of preparation ensues. But it is entirely the wrong sort of preparation, as they...

A menacing cloud is approaching the outskirts of the Known Universe, and a valiant effort is begun to save the universe from an evil demigod and army of blue lizards.