Things are going well for the Quarry Nomes since their escape from now-demolished Arnold Bros. department store, with most of the former ‘Inside’ Nomes adapting to life outside. Masklin, however, is struggling to deal with his feelings for Grimma. When he clumsily suggests that they should settle down together, Grimma instead tries to tell him that she doesn't want to be restricted by a conventional relationship, using the analogy of the South American tree frogs that spend their whole lives in a bromeliad, not knowing anything of the outside world. Masklin doesn't understand, and the two fall out. When Masklin, Abbot Gurder and Angalo De Haberdasheri subsequently take The Thing with them to investigate the nearby airport but don’t come back, it is left to Grimma to deal with a new threat; the abandoned quarry is to be reopened...