June Campbell knows exactly how her life will end. The sentient fungal parasite slowly spreading through her muscle tissue will eventually overpower her and seize control of her mind and body. But every day from now until then, it’ll make her a little bit stronger, faster, sharper. She’s already the best supply runner in Nome, Alaska. And sometimes, when she and her sled dogs are speeding across the snowbound plains surrounding the city, she can almost forget about the horrific death that awaits her and everyone she loves. Almost.
When June learns that a scientist is developing a serum that could eradicate the parasite, she volunteers to trek across a thousand miles of treacherous tundra to retrieve the materials needed to make it. Unfortunately, a blizzard soon blows her off course, right into the arms of Overlander Rafael Morales, who offers to help her in exchange for a share of the serum. June doesn’t want to rely on him. But after fending off an attack from a band of parasite-worshiping zealots, she realizes she’ll need all the help she can get if she wants to make it home alive.