Alex Caruthers ends up being Laurent Deveroux. But, although Holly doesn't know what bothers her about him, she doesn't realize who he is until they are in thrall.
People have been messing with time and that is a big no-no according to the Blind Justices. They are a higher order that maintains the balance across all worlds and times. They transport Nicole to their hall of justice and just before they decide to destroy her and her son Owen, she unveils their leader as one of the Moore family who's been manipulating things to make sure the Cahors & Deveroux destroy each other. So they kill him off, return Nicole, summon Holly and make her their new leader.
Holly is the most powerful witch who ever lived (with the possible exception of Isabeau's mother Catherine) and ends up saving everyone and the world.
That ghost/being in the castle that Nicole encountered was Merlin. Apparently there weren't just three wise men who visited Jesus, Merlin was the fourth and brought silver to bind Jesus so the world would be destroyed and he could play God in recreating it. He's been trapped in a crystal cave since the 3 wise men put him there and escapes when Sasha (Eli & Jeraud's mom) lands there by accident using his invention that allows him to time travel.
Nicole's baby Owen was fathered by Merlin and at first they think (after reading Merlin's prophecies) that he is the anti-christ and destroyer of the world but find out he's not (every 13th prophecy is a lie in an effort to get good people to do bad things). Turns out Owen is to be the savior of the world. How? Because Holly doesn't intervene in the last battle (since the blind justices are not supposed to) until she sees Jeraud trying to save Owen and realizing if she doesn't help they both will die.
Nicole ends up with Eli at the end. Phillippe dies while discovering how the 3 ladies of the lily can use the 3 Kings' medallions to trap Merlin once more.
Isabeau & Jean switch to possess Nicole & Eli. When they kill each other in battle, Isabeau & Jean bring them back to life as thank you for releasing them from the curse.
In the beginning, a warlock named Derek turns up and tells Nicole he is their on Moore family business because Sir William and James are dead and she is by default the next in line to inherit their assets. She, Owen, Robert, Amanda & Tommy move into the Moore mansion in Scarborough which hides some bad stuff but it is safer there because only Moore's and those they invite can pass through the gates.
We find out the reason behind the blood feud. Laurent's older brother Elijah & Catherine's older sister Nicole fell in love and ran away to Japan together (they have kids but are destroyed by the blind justices because a union between the two families would be too strong - I'm not entirely convinced the Moore guy in charge of the justices didn't have a hand in this). When another member of the Moore family tells the Cahors Elijah killed Nicole and the Deveroux that Nicole killed Elijah and that the other family helped the murder escape. So the Cahors switched from being warlocks who worshipped the horned god to witches who worship the goddess and Laurent & Catherine pledged to become as strong as possible to wipe the other family out.
During the battle when Alex is discovered as Laurent, he forces Holly (who is in thrall to him) to drown Jeraud. She gains control of herself too late and sacrifices to Catherine to save his life. She ends up burning some, Jeraud is alive & his scars are gone now.
Holly goes blind while she, Nicole & Amanda are trying to join the 3 medallions together at the end because she takes a fireball to the face.
Sir William surfaces and fights on Jer & the gangs side against Merlin & Laurent. Also to join Laurent's side are Catherine (Isabeau's mom - Jean kills her after he is freed) & Michael Devereoux. The goddess and the horned god show up and fight each other and kill their own people (the goddess kills Rose, the god kills Sir William) because the balance is still out of wack. They are stopped when Holly intervenes and banishes them from the world.
Kari is a walking corpse and she knows it, the Dr. Nigel who brought her to almost-life dies during the final battle with her. She dies the final death trying to stop Merlin from getting to the 3 Cahors witches as they put the medallions together. It seems through her sacrifice she may avoid going back to hell.
Jer & Holly live happily ever after in a castle in the dimension of the blind justices. Eli, Nicole & Owen seem to have a good future together because Eli is changing and likes it (but he's still naughty and it seems they'll have an explosive relationship). Amanda & Tommy will marry and take a one-year honeymoon. When they come back they will open their home as a safe house for any magic users and their friends who need shelter.
Robert (Nicole & Amanda's dad) adopts Pablo because he has no one and is still too young to be alone, he plans on teaching Pablo how to fish. Armand goes back to the church to head up the re-emerging exorcism teachings. Sasha and Luna (the head of the mother coven) are dead. Anne-louise turns out to be a Deveroux who was orphaned and the twin sister to Eve (the warlock who's been helping Jer). Anne-louise replaces Luna & Eve starts her life with Derek (the lawyer) by choosing to stay close to her sister and be of help.
While Nicole is temporarily dead and Holly is still missing (with the blind justices), Amanda has Derek use his special blood relative finder spell to locate Holly so Sasha can portal her to the battlefield. At the end, Derek reveals that Holly wasn't the only Cahors witch out there, there are more. But Nicole & Amanda decide they don't want to find them because they want to live peaceful lives.