Be Careful What You Witch For - S2-E22
Plot hole: When teenage Prue has run away with the demon, and Phoebe and Piper find her in the park, teenage Prue is 'killed'. Her sisters drive her home to get Leo to heal her, but shouldn't they have just been able to call to Leo to orb to them when Prue was first hurt, and heal her in the park, and save driving back to the Manor, risking Prue dying?
Suggested correction: I see orbing to the park but he didn't heal her, she was already dead and he can't heal the dead, that's why the genie brought her back - that's what Phoebe wished for.
But if they would have called for him right away - he would have been able to heal her before she died. However at this point in time I don't think they knew how to call for him.