Pangborn and fellow Circle member Samuel Blackwell were tasked with picking up the mundane blood that demons deliver to Valentine. One evening at the Pandemonium, they caught a glimpse of Clary Fray, whom they recognized due to her semblance to Jocelyn Fray—former Circle member, Valentine's wife, and the thief of the Mortal Cup. They were then spotted by the owner of the club and High Warlock of Brooklyn, Magnus Bane. Magnus approached them and told them they weren't welcome in his club; when he hinted that he despised the Circle for their activities and flashed his warlock eyes, Pangborn attempted to attack him but was instead caught in Magnus's invisible grip and choked. Magnus released him and forced them to leave.
After Clary left the club, they followed her to her home and, with two other Circle members, infiltrated the house and store in search of the Cup. Jocelyn refused to give up the Cup and drank a potion that knocked her out. They delivered her unconscious body to Valentine, who was infuriated that Jocelyn was delivered in such a state and without the Cup. Pangborn then told him about Jocelyn's daughter.
Some time after, Pangborn and Blackwell returned to the Pandemonium and captured Dot outside and took her to Valentine's lair in Chernobyl. Pangborn later caught her attempting to escape and attacked her. Dot got hold of one of Valentine's syringes and stabbed Pangborn in the neck with it. Valentine later found them and injected the rest of the syringe's content into his veins, thanking him for his involuntary "sacrifice".
Though Pangborn survived, the injection of the blood of another species into him left him indefinitely incognizant, and the area around his neck disfigured. Valentine kept his hands cuffed and pulled him around with a rope, and Pangborn followed him around, barely aware. When Valentine noticed scouts of the Clave spying on them, Valentine made him spew poison at them. It killed the spies and Pangborn himself. Valentine commended him for being a loyal, brave, and dedicated Shadowhunter, but pointed out that his death was for the best because his pure Shadowhunter blood had been tainted.