The Curse of The Incredibly Bad News - S1.E12

Veronica reveals that Betti is her twin sister, and that the Welkin and Krellicks are part of Betti's army, sent to destroy the remaining Guardians to prevent them interfering with her plans to blandish the Parallax. She also tells Ben that Stefan, not Jeremy, is his real father. An angry and disillusioned Ben refuses to follow her to the refuge in Forest World.