Gr. 4-6. Jeff is the least popular resident on the space station: the son of scientists, he's the only kid on board, and he always seems to be in the way or getting into trouble. Even Nanny, his creepy robot babysitter, resents him. After a rodent damages vital wiring, Nanny is ordered to destroy it, and Jeff is allowed to join the hunt. But Rat isn't just any rodent; she's scientifically modified, highly intelligent, and trained to steal information and formulas. Unbeknownst to Jeff, Rat is also an escapee-stowaway posing as Jeff's pen pal to get information and food. Short, snappy sentences, appealing characters, and tension between Nanny and Jeff combine with constant threats of ship malfunctions and Rat's struggle to survive to create a fast-paced story sure to please sf buffs. Daley left several loose ends, so perhaps readers will be treated to more stories about Rat and Jeff.