The series begins when Grace Churchill discovers her husband and mother-in-law's plan to use her newborn child, William, as a means to bring about the end of the world.
In the second movie, 18 year old William, unaware of his heritage, and having been adopted by the Adams family, finds that his next door neighbor, the witch who survived from the first film, attempts to seduce him to use his powers for darkness.
Spanner resists his heritage, preferring a normal life, but events conspire to force him to use his powers, often with the fate of the world at stake.
Beginning in Witchcraft VI, Spanner often serves as an unofficial consultant for the Los Angeles Police Department, usually working with Detective Lutz and/or Garner.
The 16th movie explains that the entire series, and its oft recasting of the leads, is part of a careful plot by Satan to control the world.
[6] "The first four movies had the pretense of a supernatural plot and an interconnected mythology, but after that, the series began to slump (or improve, depending on your point of view) in to blatant softcore pornography.