We open at the Vera estate with Maggie hearing Parker calling out to her. She goes to tell her sisters and Harry, and they agree it's promising for his humanity. Maggie thinks she may have a lead on where Parker is and wants to jump into action, but Harry wants to wait and suss out more information.
The sisters and Harry go over the prophecy of the apocolpse and try and figure out how to keep it from manifesting.
Macy gets called to the college from Galvin where there is an influx of bleeding, injured humans. Galvin says none of the symptoms are tracking with any disease, and he believes it might be demonic. Galvin then passes Macy a blood sample to study before getting called away.
Harry wonders if the Harbinger has been erased. If it becomes airborne, it will be lethal to everyone exposed and the apocolypse will commence.
Mel finds Niko in the hospital after realizing she's been effected, but she looks slightly different from other patients--she's not bleeding from her eyes or ears, only her nose. According to her scans, her injury has to do with her memeory loss, so Maggie taps into her thoughts and realizes her memories are overflowing her brain, trying to make sense of the truth about her past.
Niko's fiancee Gretta shows up and she kicks them out of the room.
Harry tells Maggie and Mel that finding Parker is their best option. Maggie thinks she can get through to his humanity and they head out on their search.
At the lab, Macy studies the blood sample. Galvin shows up asking for his help. He tells her he won't leave town until they figure out what's causing the illness. Macy realizes the virus is, in fact, the Harbinger of Death.
Maggie, Mel and Harry try and hunt down Allister but can't locate him. Maggie hears Parker calling out to her again. She touches a burned wall and gets a flash of a past event: Allister telling Parker he is on his way to becoming The Source.
Back at the lab, Galvin wants to quarentine the patients, but Macy realizes that the virus will do whatever it takes to get what it wants: tip the scale of evil.
Macy epxlains to the sisters that the Harbinger getting out is their fault. When they killed Hunter, it became airbone. They realize it's effecting everyone with evil. Macy wonders if there's a way to use her evil side even though she's broken the needle that controls her powers. Both her sisters and Harry disagree with this, worried they'd lose her completely.
Mel goes back to the hospital to find Niko. When she gets there, Mel realizes Gretta took off the ring that protects her from magic, and Niko has now turned evil as well.
In the attic, Harry thinks maybe Maggie can connect to Parker on an empathic plane. She finds him, and Parker tells Maggie they have to find Charity before Allister can--she is the last great sage and cannot die.
At the hospital, Mel clues in Galvin and Macy, who realize science isn't the answer. A cloud overtakes they realize they're running out of time.
Galvin wonders if maybe the spell he was going to use on Macy's dark side could help the infected and help tip the scales back ot tehir natural order. macy thinks it's too dangersou but he asks her to trust him.
Maggie and Harry head to a garden and find Charity. She tells them about a plant that can hide her forever, but it takes years to bloom and she needs a witch to speed up the growth. The sisters are hesitant but agree.
Parker shows up and Maggie realizes he set her up by walking her into atrap. She attacks him, and tries to break through to his human side. He ends up begging to be vanquished, but she can't follow through with it, and he escapes.
After Parker fails, Allister sends Fiona to kill Charity instead.
The sisters return to the manor and question Macy on why she hesittated to vanquish Parker. She still believes that Parker can be saved.
On a rooftop, Macy and Galvin prepare for the ritual.
In the vortex, Harry grows the plant, but Fiona finds Charity and immeidately kills her before dissapearing. With Charity dead, the apocolypse is set in motion.
Harry declares that Macy and Galvin are their only hope. They go to join them, and grab the Book of Shadows. Maggie calls out of Parker and tells him she loves him.
Allister shows up to grab Maggie and take her away.
Galvin begins the ritual. He then reveals the last step if sacrficie, and gives himself over. The infection clears, but the storm continues to get worse. It starts to rain blood.
Mel, Macy and Harry track Allister to the eye of the storm. Maggie is tied up and Allister and Fiona are performing a spell. Lightning bolts consume Fiona and she begins to die. Fiona begs for help, but Harry refuses and she dissapears, but not before the "flame" ignites.
Parker shows up and lights Allister on fire in order to save Maggie. Allister tells Parker he must take on The Source completely or Maggie will die. Parker begins to accept, but Macy ends up taking The Source on instead, and steps into the flames.
Allister drops to his knees and begs to serve Macy as The Source, but she burns him from the inside out, vanquishing him.
Maggie goes to Parker, but he leaves, feeling like he can't control the demon inside him for much longer.
Macy teleports everyone back to the manor and tells them she's wiped the minds of everyoen in town and saved Niko. They want to talk to Macy about her new powers but she jets off before they have a chance.
Macy returns to Galvins body and promises to fix him. To fix everything. She think revives him with a touch of her hand.