Engineer Daniel, foreseeing the apocalypse, sells everything he owns and builds Raven Fortress on the cliffs of the Scottish Highlands. After the virus "Grey Tide" spirals out of control, he takes in three women — nurse Charlotte, internet celebrity Isabel, and journalist Amara — to live within the stronghold. Conflicts erupt among the three women over rivalry for attention, yet they reconcile amid life-or-death crises.
Two years later, resources run low. Daniel heads out with Isabel and discovers the virus has mutated, creating zombie-like creatures known as "Hollows". They venture into the Grey Dome military base on a risky expedition to retrieve weapons. Armed with these supplies, the four fend off a horde of the infected and defend Raven Fortress.
Another two years pass; the virus fades. The group sets out to search for other survivors and eventually locates the Northern Survivors Alliance. Raven Fortress, once an isolated island, becomes a home connecting them to the rest of the world.
Tone: Grim and frigid apocalyptic survival, intertwined with human warmth within the fortress walls. Shifting between loneliness, jealous strife, rifts and reconciliation, bloody defense, and the dawn of reunion, alternating cold and warmth.
