In the first episode of a two-part story, Reese Witherspoon guest stars as Jill Green, spoiled-rotten kid sister of Rachel Green (Jennifer Aniston). Showing up at Rachel's doorstep after her parents have cut off her allowance, Jill expects her sister to help her get her life together. Alas, the old sibling rivalry roars into flame when Jill suddenly becomes very, very interested in Ross (David Schwimmer). Elsewhere, Chandler (Matthew Perry) can't cope with the fact that Monica (Courteney Cox) has both a bad head cold and an enormous yearning for his body, and Joey (Matt LeBlanc) picks the wrong time to be generous.
by Rovi synopsis