Humanity's twilight may now be at hand. With billions killed at the claws and fangs of The Brotherhood of the Fang, the leaders of the world are desperate for a victory. Hellsing, Iscariot, and Danny Phantom must unite all their powers if humanity is to survive, but their enemy is vicious and cunning. In the end, either werewolves or humans will rule the Earth.
Sir Integra Fairbrook Wingates Hellsing has been sent on a week long vacation, on order of Her Majesty. She brings Seras along as her bodyguard to Amity Park to see their old friend Danny. However, Danny himself now questions his role in the battle against evil, and no one can have a normal vacation in Amity Park.
Danny Phantom has saved the world from Disasteroid. In gratitude, Sir Integra Hellsing invites him to her home to discuss an alliance between them. But a threatening presence begins to haunt Jazz and Sir Integra. Can Danny and Seras protect them?