This OVA (original video animation) is the second animated incarnation of Hellsing, the popular Japanese comic book or manga series. Hellsing was made into an animated television series in 2002 which was broadcast here in the U.S. on Starz Encore Action channel starting in 2003. While I haven't seen the TV version, sources indicate that this new adaptation strives to be more faithful to the original manga.
Hellsing is an organization working for the British government to rid the world of supernatural creatures and things that go bump in the night. The outfit is run by Sir Integra Fairbrook Wingates Hellsing (who, despite the "Sir" title, is a woman), a position she inherited from her father. Along with the family business, Integra has acquired her father's secret weapon for fighting evil: A vampire named Alucard, which is of course, Dracula spelled backwards. Owing, no doubt, to a glitch in the Japanese to English translation, the character is called "Arucard" on the box cover, in chapter titles and on the official website. In any case, he is an extremely powerful creature, even by vampire standards.