After the events of The Dark Portal, Oswald Chitter is ill and but hours from death. While taking care of him, Oswald's parents too begin to fall into sickness. The bold midshipmouse, Thomas Triton arrives suddenly, telling Audrey Brown that she must join him on a journey to Greenwich to speak to the Starwife. Audrey and Thomas set off, followed by Twit, whom Thomas has come to regard as a best friend. Some time later, Jupiter's prison is smashed unwittingly by Alison Sedge and he swoops into the air, vowing revenge on those who opposed him...