Laddertop 3 — Orson Scott Card

All seems lost as a giant comet hurtles toward Earth, while Robbi’s Laddertop is thrown into chaos by the unleashing of Energy Spiders that now prowl the Power Web. As Robbi races against time to save the Laddertop and reveal its final secret, Azure and the rest of her research team discover the horrible truth about the comet and the existence of a different, malevolent group of aliens: The Takers.It’s up to these brilliant children to work together, using their special gifts and the unique bonds they share, to find a way to stop the end of the world before it’s too late.