A husband and wife are in a hotel on a remote islet when the sickness comes. In a matter of days the resort is overrun with the ill and the dying, all of them lost in a psychosis brought upon by the disease. The islet quickly falls, and the only safe haven is Cãlo, a southern township that the locals—the indigenous population who used to serve as resort workers—call their home.

The couple is forced to flee into La Sielve, the wildlands, and what follows is an out-and-out struggle for their very survival, a series of unnerving trials that test their bodies, minds, and their relationship with one another.

They soon learn that the islet is not the only place affected by the sickness, that it's everywhere, and that the carriers are only those with European heritage, and at first the couple—him biracial, her African-American—believe they may be immune, that they may be able to ride out the collapse. But when they begin to notice signs of the sickness in themselves, in each other, they start to wonder if they're really as healthy as they hoped.

A story of love and loss and struggle, The Mortis explores the lengths we will—and sometimes won't—go for each other during the crises we face, and delves into themes as diverse as marriage, culture, race, societal structure, and ideological rigidity.