S1·E12 Blood Sisters

With Nigel and Marianne off exploring bat caves, Eliza and Debbie are left at the ""eerie"" residence of colleague Dr. Renfield. Eliza becomes bent on spooking Debbie, but when her imagination gets the best of her the tables are slowly turned. By the time their parents return, the girls are convinced that the absent-minded Renfield is a vampire out to get them!