With extinction imminent, researchers visit an exclusive national park to observe one of the last troops of bonobo chimpanzees. Amid unusual behaviour and unexplained deaths, Shel Murray suspects her team is being hunted. Back at home, Shel's partner is attacked touring their new property. Amnesiac and quarantined, John is visited by an inscrutable doctor, tending to the still fresh wounds. As his memory returns, John questions not only the assault, but the renewed marks on his body, and the black fungus now growing on the walls.

A sudden event changes everything. Shel is interrogated over the expedition in the park; John throws himself into work, developing new software. Together, with a greater understanding of how much they have to lose, they face a grave threat, something that promises to devour everything.