Harry sets up a simulation for the sisters to practice fighting demons. They fail miserably.
Macy realizes sulfuric acid and sugar could be their way to find the Harbinger. They decide to bake cookies for Halloween.
Mel discovers that Angela Wu, her mom's student, woke up from her coma the same night they found the Harbinger's residue. She could be the vessel.
Galvin asks Macy to dinner, but she says no.
Mel gives Angela a cookie, but she doesn't react. However, as soon as Mel leaves, she disposes of the cookie. She's clearly the vessel but Mel is no longer suspicious.
Harry puts a tracker on Mel because she keeps using her powers without cause.
Maggie reveals her play to throw a Halloween party and test hundreds of people at once.
Maggie uses her powers to make Margaritas. Harry warns her about the consequences of using magic for personal gain.
The girls and Harry agree to seal the house with a spell to protect everyone while they go out hunting. Angela arrives as they prepare to do the spell. They're unable to seal the house, which means the Harbinger is inside.
Macy uses her own virgin blood as bait to lure the Harbinger.
Angela attacks and they fight. Mel uses a spell that takes down the Harbinger, but also knocks out Macy.
Harry reveals another witch that he looked after who trusted the wrong person with her secret. She was institutionalized and committed suicide. She's why he's so hard on Mel.
They have to keep Angela chained up in their attic.