This episode is very similar to the 6th season episode of Buffy the Vampire Slayer "Normal Again". In that episode the lead character (Buffy) is attacked and infected by an antagonist that creates an extremely convincing illusion to trick her into giving up her role as The Slayer.
This is the first episode of the series to feature the backyard of the Halliwell Manor which makes very few appearances across the show's 8 season run.