Jordan and the Praetor try to track down Heidi, while the Shadowhunters try to locate Jonathan. Meanwhile, Luke looks to Maryse for help and Isabelle gets a possible lead on information on what is really going on in the Clave prisons
With Isabelle's help, Simon is determined to get rid of the Mark of Cain. Now in Paris, Clary desperately tries to find an escape from her current situation. Meanwhile, Magnus tries to live life to the very fullest.