On his first space submarine voyage, Tapper Watson longs for home. He's an ordinary Erisian, not an adventurer! But when he and his new friends find themselves being pursued by trigger-happy lobster mobsters in search of the mysterious Nemo Machine, Tapper realises that he might not be quite so ordinary?

Tapper Watson is just an ordinary Erisean boy who loves adventure stories. But when one of his sixty-seven cousins sends him away on a smugglers' submarine through the River Lethe to other worlds, he just wants to go home again. On an unscheduled visit to Earth he meets Fern Shakespeare, and a talking plant called Morse, and their adventures begin. And when he finds himself being chased through worlds by a pair of trigger-happy lobster mobsters in search of the mysterious Nemo Machine, Tapper begins to realise that he might not be so ordinary after all...