Another stirring adventure awaits Art and Myrtle Mumby! With their mother returned to them and a few of her secrets revealed (she’s been around for a very long time, about 4 1/2 thousand million years, plus or minus), the family is settling into a normal life again. And their mother has decided to re-decorate, bringing their home, Larklight, up to the current Victorian standards; and so once again they are under siege in their own home. The family receives an invitation for a seaside holiday at a new resort in the Asteroid Belt near Mars, which they decide to accept. Sadly nothing is as it seems. The seaside resort has no sea until a rip in the fabric of time brings one – about every 12 hours. Jack Havoc, now a spy in Her Majesty’s Secret Service, appears to have forgotten Myrtle and is paying attention to a Miss Delphine. And their host has a dastardly secret!

Adventures and daring-do await our intrepid heroes. And it is up to Art and Myrtle, with their family and friends, to save the British Empire, again.