In order to save her child, herself, and the world as we know it, a single mother must battle a sentient fungal entity that has come to possess the body and mind of her seven-year-old daughter in this chilling and unforgettable new novel from the acclaimed author of The River at Night and Girl in Ice.

In the rainy northeastern suburbs of Boston, where humidity lingers and fungal blooms emerge in damp corners, Dani, a single mother and scientist, reckons with a disturbing behavioral change in her young daughter. She's desperate to understand: what could have triggered this? Is it an early onset of a psychological disorder that runs in the family...or something far more sinister?

And?yet more frightening?can it ever be stopped?

The truth may alter everything Dani once believed possible in this dark and unforgettable new novel.