"Kirkus Reviews" calls this book for 8-to-12 year-olds "A charming tale . . .with a strong dose of humor." Henry, a grandfather with PTSD from combat decades earlier, is startled to find a strange boy, Squiggly Squires, standing beside him in the woods behind his country home. Squiggly says he came to Henry's world of Out from his world of In and points to a small hole in the hillside with water trickling from it. Henry is sure he is hallucinating again. But unlike other episodes, this one quickly proves to be pleasant. Squiggly tries to explain to a skeptical Henry that by entering that hole he will enter the cave world of In. Why is Squiggly here, Henry asks. Because, Squiggly says, he has been chosen to find The Gift and bring it back to In to be replicated. Squiggly likes Henry and pleads with him to come along on the trip. And how can Henry do that? Simple, says Squiggly. Just say the magic words, believe, and then say "Unform." This begins fabulous cave adventures for Henry and Peggy his granddaughter as they visit the Squires family who live in the troglobite (entirely dark) zone of caves. All cave forms are scientifically accurate, as are the strange animals the characters encounter such as pseudoscorpions--all blind and depigmented. Creatures are greatly magnified from their actual size and are either likeable or ferocious. The Gift turns out to be at first a heartbreaker, and then a delight in disguise. Although those who enter In initially are stressed, by courageous and inventive action they survive to return to Out much for the better.