Exchange Rate

Hal Clement also has a rich and lively imagination, especially when it comes to alien lifeforms, and he has created some of the most memorable alien characters in science fiction. Clement's outdone even himself in the suspenseful novella, Exchange Rate, in which harried human explorers (under pressure in more ways than one!) must try to figure out the lifeways and motivations of some extremely strange and enigmatic alien creatures on one of the strangest planets ever portrayed in science fiction - and do it all before the clock runs out.