The Tree of Life (S03E19)

An upscale fertility clinic hides a dark secret, operated by a cult of female Druids. They utilize a cursed fertility statue to increase their numbers. When couples struggling with infertility seek help, the Druids perform a deadly ritual that claims the husband's life, resulting in the birth of twins: a boy and a girl. The mother is misled into believing she has only delivered one child, as they keep the girl to groom as a Druid priestess while handing over the boy. When a friend of Micki's seeks treatment, the trio investigates the clinic, managing to destroy the statue before the Druids can enact a ritual to duplicate it. With the leaders of the cult defeated, they successfully reunite the girls with their biological mothers.