Putting Up Roots — Charles Sheffield

When Josh and his autistic cousin Dawn are sent to the planet Solferino, they join a group of kids already working for an interplanetary conglomerate stationed there. Assured by the bosses that no intelligent life exists on Solferino, Josh and Dawn come to suspect otherwise. Especially when Dawn makes contact with one of the creatures, a creature with whom she shares a mysterious ability to communicate.

With the corporation pressuring them, Josh and Dawn are drawn into a battle to save the creatures. And, it turns out, to save themselves.