After a family adopts an abandoned baby rabbit, Bunnicula, mysterious happenings lead the family cat Chester (voiced by Howard Morris) and dog Harold (voiced by Jack Carter) to suspect their new peer is a vampire.

When Amelia (voiced by Nancy McKeon) is kidnapped by Mordo the warlock (voiced by Hans Conried), Miss Switch (voiced by Janet Waldo) returns to help Rupert (voiced by Eric Taslitz) rescue his friend.

Saturna the wicked witch (voiced by June Foray) is the real power behind this diabolical plot. Amelia begins to fade away and vanishes – a disappearance Miss Switch knows will be permanent, unless Amelia is rescued by nightfall.