As Billie investigates another theory behind her sister's disappearance, her emotionally distant parents arrive for a visit, and the mild manner pair are accidentally transformed into cold-blooded killers. Meanwhile Piper is reluctant to leave the house for fear of leaving her children without a parent, in wake of Leo's absence. Phoebe gets a bad case of writer's block; Paige finally connects with Henry and Billie learns that her parents never stopped searching for her sister.