With the Halliwells' help, Billie attempts to help Christy reintegrate back into everyday life and to gain control over her powers. Billie and the Halliwells are unaware of Christy's collaboration with the Triad. The Triad identifies Billie as the Ultimate Power, which was foreshadowed in earlier episodes as the season's big bad, and refers to Christy as the key to unlocking Billie's power. The Triad arranges for Christy's parents to be killed by a pair of Noxon demons (John Rosenfeld and David S. Lee), believing prolonged contact with them could sway her morality to the side of good. Billie becomes angry by the Halliwell sisters when they decide to interrogate the demons to gather more information about the Ultimate Power rather than killing them to avenge her parents' deaths. Christy uses Billie's feeling of betrayal to turn her against the Charmed Ones. Billie and Christy vanquish the Noxon demons, who were previously believed to be invincible, and the Halliwell sisters realize that Billie is the Ultimate Power.