Magnus awakens to find her home and Sanctuary is in a terrible shambles. The roof has collapsed, allowing rain to pour in all over; the power is gone, and there are various wild plants growing all over the inside of her mansion. When Magnus looks outside, she’s alarmed to see that the devastation is not limited to the Sanctuary. The surrounding city also lies deserted and in ruins, destroyed by some unknown natural--or unnatural--cataclysm. Trying to find out what happened, Magnus strikes out into the ruined city, where she winds up having a frightening encounter with a group of marauding, zombie-like savages--one of whom tries to sting her with a strange tentacle that emerges from his mouth. Just before she becomes one of them, Magnus is saved by a band of survivalists, led by a battle-scarred Will.

But her saviors treat Magnus little better than the monsters, forcing her to strip and shower in a scene that is extremely unbearable to watch. Will isn’t convinced that this is the real Magnus, but instead a shape-shifting imposter who has taken her form. The "real" Magnus whom Will knew was killed in Buenos Aires, trying to fight the plague that had ravaged the world, infecting both human and abnormal alike, and turning the majority of the population into these murderous savages who exist only to feed. Magnus takes it upon herself to try and find the cure, desperately going through her old video logs and examining a newly turned patient, while the hordes of monsters descend on the remnants of the Sanctuary like demonic locusts.

Pavor Nocturnus is an unrelentingly grim nightmare that’s set in a very bleak, post-apocalyptic world ten years hence, where there are no quick solutions. The series’ reliance on CGI sets really works very well here, as we see a completely wiped-out, shattered landscape that’s as gray as the permanently overcast skies. There’s no relief; Magnus is provided with no easy answers as to how she got there--at least until the very end. And the revelation as to how it all began is a shocker. But until then, PN is nothing more than a marvelously dark run through the dark places of the soul, where nothing matters but an inexorable struggle to stay alive. This episode is a very nasty "what if" that’s actually a relief to awake from.