Hellsing is an organization dedicated to protecting England from supernatural threats. When a village is overrun by ghouls created by a vampire, Sir Integra Hellsing sends her most powerful weapon, the vampire Alucard, to investigate.
During the mission, Alucard encounters a police officer named Seras Victoria and transforms her into a vampire. Now a fledgling, Seras must grapple with her newfound existence as she joins Hellsing in their fight against the darkness.
The anime follows Alucard and Seras as they battle various supernatural enemies and Seras's struggle to adapt to her life as a vampire fighting alongside humans.