Reagan Darby crams her dad's urn into an overflowing backpack. His last wish: deliver the urn to Rocky Mountain National Park and release his ashes into Lake Nanita. To find closure, she'll hike the same route they completed after her latest involuntary stay at the hospital.

But not alone, as she'd hoped. Her cousin Dalton surprises her at the trailhead and insists on tagging along. Soon, his eerie stares and half-volume mutterings set her on edge. As they trudge further into the mountains, dodging moose and lightning strikes, she catches him rifling through her backpack multiple times. She confronts him, but he shrugs it off. His claims that he came along for support wear thin, but she's too deep into the park simply to turn around.

When Reagan discovers a hidden compartment in the lid of the urn, a tiny silver key tumbles onto the floor of her tent. But there's no telling what lock the key might open. More unsettling, however, is that her lithium has gone missing. With only a meager Swiss Army knife for protection, she'll have to fend off her cousin, resist the creeping mania, and escape the forest to find the lock. If the man Dalton works for locates it first, he'll reduce Reagan to the same pile of dust and ash.

Reagan's Ashes combines wilderness survival thriller with amateur sleuth mystery.