S7, E4: While Darrin sits in jail, Samantha finds out that the bedwarmer is actually a warlock trapped by one of the witches. Sure enough, the culprit is Serena. Samantha sends Serena back in time to get the spell used to transform the warlock in the first place. With one situation out of the way, Samantha faces another one- getting Darrin cleared of a crime he did not commit.