The 17-year-old best friends are neighbors in a flyspeck California town in the Mojave Desert. Tamma, who lives in a trailer home, is the black sheep of her dysfunctional family, but she carries herself with the motormouthed swagger of someone determined “to be the best trad climber that has ever lived.” Dan is a gifted kid whose upbringing has been more sheltered. His mother is a former novelist whose career stalled due to a congenital heart defect. She and Dan’s father are pushing him toward college and a stable career, but, like Tamma, Dan is addicted to the exhilaration and challenge of climbing. The two meet regularly to take on a terrifying nearby boulder. They have no money for gear—not even a mat—and rely on the other to catch them if they slip. It’s a trust-fall exercise ramped up to a death-defying degree.