When Toby stumbles upon Orvis - an obsolete robot - he is about to shut himself down... forever. Toby knows how Orvis feels: no one wants her either. A spacer all her life, her too-busy-for-Toby parents have packed her away to school on Earth. But when her domineering grandmother decides to send her to school on Mars, Toby rebels. With Orvis and her only other friend Thaddeous - a lonely castoff too - the trio set off in search of sanctuary with her great-grandmother.
But to get there they will have to cross The Empty.