Down from Cascom Mountain is set in Leah, New Hampshire, the town that Ann Joslin Williams’s father, the writer Thomas Williams, invented in his fiction. Leah is a rural town next to Cascom Mountain, filled with beautiful but dangerous trails and cliffs. Mary Hall, who worked two summers at the local mountain lodge as a teenager, discovered the body of a boy who died of hypothermia. And a decade later, Mary watches helplessly as her new husband, Michael, plunges to his death from one of the mountain’s treacherous cliffs. Mary is left by herself in Leah --- except for Tobin, a teenage neighbor who appoints himself Mary’s protector.

Callie is a teenager who has a lot in common with Mary --- she has the same job at the lodge that Mary had at her age. And like Mary did at her age, Callie is sleeping with the crew boss at the lodge. Both Mary and Callie develop crushes on the same man --- Ben, the fire watchman who lives in solitude at the top of the mountain. When Callie suspects that she is pregnant, she finds she has no one to turn to --- Mary has found solace from her grief in Ben’s arms. In her desperation, Callie loses her way on Cascom’s winding trails, and she must use her wits to make it off the mountain alive.