Colin MacLeod, an immortal Scottish Highlander, is joined by the sharp‑tongued ghost Amergan as they hunt the immortal tyrant Marcus Octavius, who killed Colin’s lover on the Celtic plains centuries earlier. The city of New York, once a great metropolis, now lies beneath the water, with only a single towering fortress, Octavius’s stronghold, looming above the sea. MacLeod must decide between rescuing the surviving inhabitants of New York and confronting the despot he has long awaited.