Tyler's Folly: a colony world on the unattractive side of Earthspace, a planet wracked by earthquakes and crawling with off-world bodysnatchers. When the local authorities pull a bedraggled Professor Bernice Summerfield out of the ocean in an off-limits 'quake zone, they naturally want to know what she is doing there... but the professor can only mumble something about woolly mammoths and sabre-toothed tigers.