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.

Continuing to track down information on the rumors about misconduct at The Clave's downworlder prison, Isabelle asks Alec for help. Meanwhile, Magnus succumbs to asking Lorenzo for a favor and Jace takes Clary on a special date.