Millfield is not an ordinary town. Beneath it lies something ancient, patient, and angry. Harrison Hollow knows the danger and why his grandfather built a concrete silo in his cornfield, not to store grain, but to seal a rupture between worlds of light and shadow. For a century, the structure held. Now it is crumbling. Civil engineer Phoebe Weaver is tasked with overseeing the demolition of the silo, but Harrison insists doing so will unleash the horror it was built to contain. Sentient shadows. Armed with data, structural reports, and science, she rejects such a notion and goes forward with the demolition. Within days, shadows detach from the people who cast them. Panic and terror spreads. Darkness pools in daylight, town elders turn violent, and something emerges that cannot be explained. Phoebe and Harrison team up to stop the Shadow Walkers before they destroy the town...and beyond.