After the sisters save a doctor from the Source's personal hitman, they're exposed as witches. As a result, Phoebe and Cole get trapped in the Underworld, where they reluctantly make an agreement with the Tempus to go back in time to before the sisters' secret is exposed. However, that causes Phoebe, Cole, and Leo to be stuck in the Underworld while Prue and Piper get sent back in time and get caught in a life or death situation while Phoebe is forced to make a difficult decision to stay where she is or to go help save innocents and her sisters.