Charmed - Season 4 Episode 16 -

The Seer gives Cole a potion hidden in chocolates so that Phoebe will conceive a son. When Piper and Phoebe save the life of the innocent columnist Karen Young, Phoebe has a premonition and realizes that Karen has been attacked and infected by a ball of light of a demon. Meanwhile, Paige unexpectedly arrives at home and sees Cole using demonic power on Karen. She tells Piper, who does not believe her. Cole sends a demon to infect Paige and destroy her credibility.