Problem on Balak

A small exploratory crew visiting a distant, apple-sized planet discovers an intelligent, octopus-like species that speaks Terran and maintains complex ecological symbioses. They are introduced to a long-marooned Terran and then confronted by a duplicate who insists he is the original, while the natives claim one of the pair is an alien mimic. The natives say the dilemma is a deliberate test that requires a species to understand itself; the crew is rendered unconscious and taken into the settlement. The story centers on a puzzle of identity, cultural ritual, and interspecies cooperation amid the perils of fieldwork.