What would the world look like in the grips of a highly contagious virus causing mental illness? What if that virus, created as a weapon by our own government, leaked before completion of a crucial antidote? When faced with that very situation in The Enemy Within, the US military activates a brutal containment strategy— a grisly soldier named Fox. As Fox hunts contacts of the virus, he also becomes infected. His only hope for a cure is to protect the two people he was sent to kill, Jack and Claire. The trio hide away to buy time for Jack, an imminent virologist, to develop an antidote. As a trained psychotherapist, Claire attempts to keep the group grounded while the virus leads them all further from reality. Time runs thin and paranoia mounts as the group faces multiple threats. But which threat will prove to be fatal? The military tasked with hunting them down or what lurks within causing an inevitable psychosis?