The chamber in the sky

In the future, the world is falling apart. Invaders from space, the Thusser, have pushed New Norumbega to the brink, and if it falls, so will Earth. Brian, Gregory, and the regal Gwynyfer must find a chamber, floating in space for years, that can turn the Thusser off for ever. All they have to do is find it in the myriad odds of space.