Father Hubbard tracks down Diana and Matthew and reunites them with Jack, now a young adult vampire. Hubbard sired Jack as he lay dying from plague, and thus he passed on the blood rage he carried from his own sire, Benjamin. When Baldwin comes to London, Jack feels threatened and attacks him, revealing not only his condition but the fact that he is the Oxford killer. Baldwin orders Matthew to kill Jack, but Matthew's hesitation allows him to escape. Hubbard reveals that Benjamin has been stoking Jack's rage, exploiting his desperation to find his family. Matthew locates Jack and brings him home to Diana. Defying Baldwin in this way leaves Matthew no choice but to seek independence. Chris and Miriam have made progress in their studies of vampire DNA, but to find a cure for blood rage they need more samples and additional resources. Matthew reluctantly agrees to let a group of student researchers join the project after signing a non-disclosure agreement. Matthew, Marcus, and Jack leave for New Orleans, home of Marcus’ surviving vampire children, to obtain their DNA and seek their cooperation in forming a scion. Benjamin, now united with Gerbert, calls Matthew and sends him video evidence of Jack's crimes, demanding to meet with him and Diana.
After weeks in New Orleans, Marcus’ attempts to win over his offspring have been unsuccessful. Jack continues to experience blood rage, while Matthew tries to help him learn control. Back in London, Phoebe and Diana have been tracing the history of all the books belonging to John Dee. They identify an occult text at the British Library which Diana uses her magic on, revealing that one of the missing pages from the Book of Life is in Father Hubbard’s possession. Peter Knox had already made a visit to Hubbard's office, resorting to his usual threats. Explaining what lies at stake for all creatures, Diana persuades Hubbard to trust her with the page. Sarah feels useless in the current fight and tries to sneak away. Gallowglass reveals to Sarah that he has watched over Diana since birth, at Philippe's command, and convinces her that Diana still needs her. Marcus manages to get an audience with Ransome, the head of his vampire brood, who will talk to Matthew only if he takes responsibility for what he did. Matthew recalls the name and face of every vampire he killed in New Orleans, including Ransome’s mate, and apologises sincerely to both Ransome and Marcus. Benjamin approaches Satu at the Congregation headquarters, hoping she will join him and Gerbert in the fight against Matthew and Diana, but Satu has her own plans.
With a lead on the third missing page, Diana crafts a locator spell, which she and Sarah need assistance to cast. Diana visits the site where Goody Alsop's house once stood and meets Linda Crosby, who leads the local coven and honors Goody's legacy. The spell leads Diana to the daemon Timothy Weston, a frightened recluse who considers the page part of his family and will not surrender it. Armed with additional DNA samples from the New Orleans vampires, Chris discovers that the gene for blood rage is activated by something within the human genome, and thus depends on the genetic makeup of the individual being sired. Miriam brings the news to Matthew in person, convincing him that even without a cure, he cannot let fear of failure keep him from returning home. Agatha accompanies Diana on a return visit to Timothy, promising the troubled daemon that he will no longer be alone. Having secured the page, Diana goes into labor. Matthew officially requests Baldwin's permission to form a scion, but his brother refuses to give it. Matthew then rushes back to London, joining Diana as she gives birth to a girl and a boy. Gallowglass, having confessed his love to Diana, realizes the time has come for him to leave her side. Agatha goes back to Timothy’s house only to find him dying after an attack by Peter Knox.
Agatha and Diana attend Timothy’s funeral. Ysabeau and Marthe arrange a celebration at Sept-Tours for the twins’ christening. Diana discovers that baby Rebecca needs blood instead of milk, while Jack and Matthew hear baby Philip’s witch blood singing. Gerbert pressures Baldwin to bring the children before the Congregation so their nature can be determined. Baldwin disrupts the christening ceremony and attempts to subdue Matthew physically. Diana promises Baldwin that any blood-raged vampire within the scion will learn to control it or be spellbound. Baldwin grudgingly gives his permission, but he reminds Matthew that Benjamin is now his responsibility. Benjamin has become obsessed with having his own child and is kidnapping and raping witches. He allows one to escape and make her way to Sept-Tours in order to lure Matthew into a confrontation. Among the witch's things, Matthew finds a watch engraved, "To Philippe 1922". Marcus wants to strengthen the Knights of Lazarus with more members who can protect each other if the Congregation comes for them. Diana and Matthew pledge on behalf of the twins, with Miriam, Jack, Sarah, and Chris joining the ranks as well. Matthew also welcomes Fernando into his scion.
Matthew leaves to confront Benjamin, alone. Diana, Sarah, and Fernando go to Oxford, and Marcus instructs Fernando to bring Gallowglass back into the fold. Marcus also gives Phoebe a chance to leave in case things go wrong, but she is determined to stay with him and become a vampire. Ashmole 782 appears again for Diana and she replaces the missing pages. The Book transforms itself; the pages become blank and the text now lives within Diana. Peter Knox confronts them at the airport, but Sarah uses a spell Diana crafted to kill him. Matthew finds Benjamin in Poland at the site where Philippe was tortured and learns that he was directly involved. Matthew defeats Benjamin in a physical fight, but Satu intervenes and knocks Matthew unconscious. Gerbert reveals to Domenico that he has conspired with Benjamin for centuries to slowly destroy the de Clermonts. Surprising even himself, Domenico shares this information with Baldwin. Diana writes furiously, pouring out information from the Book of Life that Miriam and Chris recognize as central to their genetic work. Marcus receives a video from Benjamin in which he directly addresses Diana, revealing that Matthew is under his control and on the verge of death.
Baldwin recognizes Philippe’s watch on Benjamin’s wrist in the video, making the connection to the place where his father was tortured. Diana departs for Poland with Baldwin, Miriam, Marcus, and Gallowglass. Confronted by illusions crafted by Satu, Diana sees through them and spellbinds her fellow weaver. She then advances on Benjamin, weaving the tenth and final knot to end his life. Matthew is too far gone to be helped by anyone’s blood but Ysabeau’s, so they transport him back to Sept-Tours, where he slowly recovers. Miriam and Chris have pieced together the genetic information Diana gained from the Book of Life and discovered the reason creatures are in decline is precisely because they have been segregated. Interbreeding is the key to their survival. Diana takes over as the de Clermont representative to the Congregation and convinces all but Gerbert to repeal the Covenant and elect Agatha as their new leader. Baldwin and Matthew reconcile, Fernando is officially recognized as Hugh’s mate, Phoebe and Marcus get engaged, and Agatha is reunited with her family. Diana writes the twins’ lineage into the Book of Life.
Glad the series was finished but as a viewer you had to do a little work to figure out where to find and watch it as initially it was on AMC, then season 2 and 3 were filmed back to back, then COVID happened and there was at least a two year delay between season 1 and 2.