Author Philip Reeve was shortlisted for the Whitbread Prize Children's Book Award. In 1851 a mysterious visitor to Art Mumby's space home has plans for a calamity that will destroy not only the entire British Empire, but also the known universe. Can disaster be prevented with help from Art's irritating sister Myrtle, a few exotic space creatures, and an extraterrestrial pirate?

At the edge of space, a mysterious cloud appears. The last transmission from a remote outpost near the cloud warns of grave danger. Now Art, Myrtle, and the rest of the family launch an investigation-and what they find is so horribly, terribly monstrous that not even a billion mothballs will keep it at bay!