Thirteen-year-old Perrin Hollis sees patterns other people miss, in leaves, in rock, in the spin of his old spirograph toy. So when he finds strange spiral-and-dot markings deep in an Ozark cave, he knows they're not random. His father isn't so sure.
But the deeper Perrin looks, the more he's certain: the marks aren't separate drawings. They're pieces of one map, a map written in the stars themselves, left behind by people who wanted to protect something sacred long before anyone alive was born.
There's just one problem. The land is being sold, the bulldozers are coming, and someone else has figured out there might be treasure in that cave, and he doesn't care what he destroys to get it.
With the solstice sun the only key that will ever unlock the map's final secret, Perrin has days, not weeks, to prove what he's seen, before the mountain, and everything it's kept safe, is gone for good.
He was the only one who saw it. He may be the only one who can save it.