The summer before Troy Stotts turns seventeen, his mother dies. Communicating with his father mostly by notes, Troy spends his time with his friends: Tom Buller, brash and fearless; Gabe Benavidez, smart enough to know he'll never take over the family ranch; and Gabe's sister, Luz, who Troy has loved since they were children. They want this to be the summer of "ghost medicine," when time seems to stop, and they can hide from the past and the future, and all the ghosts that come with them. Troy and his friends don't want trouble, but as the summer fills with dangerous and fateful encounters, can even the most powerful ghost medicine keep them hidden and safe?