Jonathan is holding Valentine hostage in the basement of a remote cabin. We briefly see a flashback of him returning to the world.
Maia checks up on Simon after his latest troubles with Clary. Simon plans to celebrate Yom Kippur with his family to atone for sins and get his mind off the drama.
Isabelle and Alec's father Robert returns to the Institute as Envoy for the Clave. He announces that Alec will stay leader of the New York Institute (for now), but he must work on finding Valentine. He lashes out at his father over his father's affair.
Jace believes Valentine is hiding away in Idris and needs a warlock to find him. Clary, however, starts to have a vision about the lake outline on the map. She draws the outline as a rune and it opens a portal to Idris.
Jonathan reveals what happened to him with the demon. He had made a deal with Azazel to escape and plotted an attack on the Shadowhunters.
Clary loses her stele in the lake. She starts to feel dizzy and unable to stand.
Isabelle confronts her father about him yelling at Max. Her little brother read classified fire messages from the Inquisitor.
Maia invites herself to Simon`s family dinner. She pretends to be his girlfriend, and his grandmother is impressed.
Isabelle and Alec discover the disturbance in Jace's office. Meanwhile, Clary hears screaming coming from the woods. She finds a bloody mess.
Jonathan blames his first murder as a simple experiment. He is mad that Valentine got rid of him to protect another child.
The dinner hits a few snags as Simon's mother wants everyone to reveal what they're atoning for. But, they seem to really like Maia.
The group discovers that Jace and Clary portal'd to a dangerous lake in Idris. They're not sure how a portal was created within the Institute, and how it left shards inside. Isabelle will be heading there to help them.
Ethereal returns and he looks younger. He's rejuvenated and tells her that Jonathan is still alive.
At the dinner, Maia reveals that she's doing online classes to become a marine biologist. She hasn't talked to her family in years after running away. Simon is unable to come clean about his regrets.
The lake water causes hallucinations and unless Clary is cured, she could lose her mind forever.
Jonathan plans to send Valentine to Edom.
Clary's hallucinations get worse and she fights Jace and Isabelle. It's not until Jace's run activates that she's cured from the water.
Alec's father sent the fire messages to Imogen so that Alec could be kept leader of the Institute. He had done so by threatening to reveal the Clave's biggest secret: They never recovered the Soul Sword. In actuality, Jonathan has the Soul Sword.
The group enters Valentine's cabin and finds no one.
Jace is looking over old books from Valentine's cabin. Clary deduces that her brother Jonathan is still alive and the angel message wasn't a dream.
Jonathan didn't send Valentine to Edom. They're hiding together in the same apartment.