What episode is this(3)?

Paige casts a protection spell on an Innocent when Sirk, a Demon-Mortal Hybrid, tries to kill him to become fully demon. The spell goes wrong and the Innocent can't die. The spell blocks all deaths, and the Angel of Death recruits Piper to catch up the damage the spell has done.

ay the name of the episode and also what season it's in to win 10 pujian - only 1st correct answer gets the props!!!!:)