One more detail:
When Hellsing rescued Claude, they were able to use him to track the movements of the vampires who had been sucking on him, in the same way that Abraham Van Helsing originally used Mina to track the movements of Dracula about forty years before.
This nuance is, of course, completely lost on Bertie.
Narration: Then Jeeves explained it all to me. It seems my dear cousins Claude and Eustace both fell head over heels for the same lovely young filly, who also happened to be a vampire, luring them in to be a snack for her stronger but less charming sire.
The chaps at Hellsing charged in and rescued Claude, but the vampires scarpered, the younger with Eustace in tow. She bamboozled everyone at Aunt Dahlia’s so she could hide there, not realizing Hellsing was already on to her.
They let her be at first, so she wouldn’t get wise and call her sire for help. When the sire thought he had escaped, Arthur sent Jeeves off to catch him by surprise.
The young one could tell, somehow, who had killed her sire; but she didn’t realize Jeeves was connected to her hideout, until Aunt Dahlia said his name…
Jeeves: Sir, you seem remarkably unsurprised by all of this.
Bertie: What, Claude and Eustace both falling for one unsuitable woman? Happens about once a week.
Jeeves: I was thinking of the vampires.
Bertie: I say! Haven’t I always said I believe you could handle anything? Why should that not include vampires?