Cupid is forced to call on the Halliwells for help when the demon Drazi steals the ring which gives Cupid his powers. Recent matches are already being disrupted by Drazi, and the longer he has the ring, the more and older relationships will be destroyed. Prue and Piper have vested interests in helping, as they have their own recently formed love connections to protect. As for Phoebe she seems to be falling for cupid himself, but in the end has to be satisfied with a thank you kiss.
Ginny Owens: I Wanna Be Moved (from the album Without Condition) First scene after opening credits
Melanie C: Ga Ga (Northern Star) Scene with Piper, Prue, Jack, and Dan at P3