A round trip to Vanaris, the Donkey Planet, would take 17 years at the speed of light--but how about the speed of thought? Space Center chief Eks explains to young scientists Jason and Frank that a Vanarian boy and a donkey will be provided for their unprecedented trip, but they don't realize until they have already been thought-sent there that Jason has been given the boy's form and Frank the donkey's. Their assignment is to deliver an aluminum sample to scientists on Vanaris and to bring back some of that planet's extremely heavy metal, quundar. To do so the two must elude Vanaris' dreaded police chief Gru--who does alas get wind of the alien presence and stations guards along their route. The problem: only from their landing spot can they think themselves back to earth and their own human shapes. But the daring ruse Jason comes up with when faced with Gru is only routinely ingenious, and despite the donkey trans-formation none of this has the nimble humor of first-class Corbett.