Simon is determined to get rid of the Mark of Cain and, with Isabelle's help, tries to track down New York's oldest vampire to get more information on the mark. Now in Paris, Clary desperately tries to find an escape from her current situation. Meanwhile, with his new sense of mortality, Magnus tries to live life to the very fullest.
- Katherine McNamara as Clary Fairchild
- Dominic Sherwood as Jace Herondale
- Alberto Rosende as Simon Lewis
- Matthew Daddario as Alec Lightwood
- Emeraude Toubia as Isabelle Lightwood
- Alisha Wainwright as Maia Roberts (credited only)
- Isaiah Mustafa as Luke Garroway
- Harry Shum Jr. as Magnus Bane
- Luke Baines as Jonathan Morgenstern
- Pasha Ebrahimi as Cain
- Lola Flanery as the Seelie Queen
- Jade Hassouné as Meliorn
- See more here
A list of the songs and score music featured in this episode:
- "The Chain" - Mattis
- "Le Rendez-vous" - Lydia & Sebastien
- "Toujours du Soleil" - Antena
- "Carry You" - Ruelle ft. Fleurie
- Some scenes for this episode were shot in Paris. Filming for these scenes took place in May 2018, after filming of City of Glass. Only Katherine McNamara, Luke Baines, and Dominic Sherwood shot their scenes in Paris, and Matthew Daddario and Isaiah Mustafa were edited into the scenes.
- "What episode is the scenes that were shot in Paris?" "312!" Todd Slavkin response on Twitter
- "Missing our cast as they are shooting in romantic Paris this week." Kathleen Jenkins on Twitter
-   — Photos of filming taken by a fan | VK
- Katherine McNamara's Favorite Relationship on 'Shadowhunters' Isn't The One You Think It Is | Just Jared Jr.