After her mother disappears, Clary must venture into the dark world of demon hunting, and embrace her new role among the Shadowhunters.
Cast:Katherine McNamara , Dominic Sherwood , Alberto Rosende , Matthew Daddario , Emeraude Toubia , Isaiah Mustafa , Harry Shum Jr. , Alisha Wainwright , David Castro , Alan Van Sprang , Nicola Correia-Damude , Jade Hassouné , Maxim Roy , Anna Hopkins , Luke Baines , Joel Labelle , Will Tudor , Chai Hansen
Secrets abound as the Shadowhunters and Downworlders try to get back to normal after Valentine's death. Clary struggles with keeping her secret about Raziel's wish, while Alec pushes Jace to come clean about whatever Jace and Clary are hiding. Luke must use tough love to keep his secret hidden from Ollie who is on a war path for answers. And Magnus hides his true feelings about his new position in the Warlock community from Alec. Meanwhile, Lilith sets a plan in motion in New York City as Simon spend stime in the Seelie Court.
With the institute under siege by a greater demon, tensions between shadowhunters and warlocks are higher than ever as Alec tries to remain in control of the situation.
Simon tries to enter the Seelie realm whilst Raphael faces a heartbreaking loss. Jace has a suspicion about who this new, unknown Greater Demon may be, which has been nicknamed the Owl. Alec hosts a family dinner with help from Magnus.
Alec doubles his efforts to find the Owl. Jace begins to fear his hallucinations may hold roots in his past and turns to Luke for guidance.
Someone is out to get Simon and Jace is on the hunt to find out who it is, meanwhile Clary turns to Luke to find a way to help Jace. Alec worries about the future of his relationship after learning more about Magnus' romantic past.
Clary teams up with Magnus to investigate a recent demon attack. Simon is stunned when he's visited by someone he never thought he'd see again, and who now won't seem to leave. Meanwhile, Izzy worries about dinner with her family and a special guest and Luke reaches out to Maryse.
With the Owl's identity revealed, Alec, Isabelle, and Clary head to Alicante to try and find a way to stop him. Luke and Simon team up to track Lilith's latest possible victim. Maia reflects on her past.
Clary awaits judgment while imprisoned by the Clave. Magnus, Alec and Isabelle try to save Jace. Simon learns more about the queen of Edom.
Clary offers the Clave something it wants in return for sparing her life, with disastrous results. Simon's past returns to haunt him and his family.
Simon makes a heartbreaking choice to protect his family. Magnus asks his father for help. The Shadowhunters prepare for a showdown with Lilith.
Jace is free of Lilith's control, but the aftermath of the battle has everyone reeling. Simon is determined to rid himself of the Mark of Cain once and for all while Clary tries to escape an unfamiliar captor.
Simon tried to track down New York's oldest vampire to get more information on the Mark of Cain; now in Paris, Clary desperately attempts to find an escape from her current situation; Magnus tries to live life to the very fullest.
The Jade Wolf pack is devastated after Heidi's attack, leaving Jordan and Maia in a corner. Jace encourages Clary to take a break from hunting Jonathan, not realizing that Jonathan has returned to New York. Magnus goes to Lorenzo for a favor.
As news of the vampires' attack on the Jade Wolf spreads, the Shadowhunters spring into action to stop the culprit. When Heidi concocts a plea deal, Maia considers taking justice into her own hands.
Clary and Jace come up with a risky plan to get rid of her twinning rune, which may bring an old enemy back into the fray; Alec worries about Magnus.
Simon and Izzy team up on a secret mission to figure out what the Clave is hiding; Clary becomes conflicted about Jonathan as the Shadowhunters try to get answers.
A demon outbreak in New York City on Halloween becomes a top priority at the Institute, but as the Shadowhunters hunt the demons, Jace becomes more worried about Clary. Meanwhile Alec has to juggle the outbreak with his deep concern about Magnus' depression
In order to win Clary back from the darkness that's overtaken her, Jace joins Clary and Jonathan on their quest for the Morning Star sword. Izzy, Luke, and Simon try to remake the sword Glorious. Magnus is surprised to see his father in New York.
Alec, Jace and Isabelle make a plan to finally get Clary back and stop Jonathan, much to Luke's and Simon's chagrin; Magnus struggles to deal with his father's reappearance; Maia must make a tough decision that could affect the rest of her life.
As Jonathan grows in power with a new ally by his side, the Shadowhunters and Downworlders must combine their powers, venture to Edom and stop their foes before they destroy the Shadow World. Wedding bells are in the air for one special couple.
With his new power, Jonathan wreaks havoc on the Shadow world, targeting institutes around the globe, and Clary must make a great sacrifice in order to hopefully stop him for good. Meanwhile, wedding bells are in the air for one special couple.