S1·E5 Double, Double, Toil and Trouble

Stopping to rest in the valley below Mildred comes upon a group of witches & hears them planning to take over Cackle's Academy! Mildred, thinking on her feet, turns all the evil witches into snails. Back at school, while Miss Hardbroom does not believe Mildred, Miss Cackle recognizes the description of the Chief Conspirator as her wicked & jealous twin sister, AGATHA.