Jem was seventeen when he first met Tessa Gray. He and Will were investigating the death of the mundane Emma Bayliss, which led them to the Dark Sisters, though Jem was not part of the raid on their housesince he was too ill. … 展开

Jem, Will, and Tessa visited the York Institute to find out more about Mortmain's history and why he was so determined to kill Shadowhunters. Jem gave Tessa the Carstairs family ring as an engagement ring so she can pretend that … 展开

It was revealed after a fight that Jem had been taking twice as much of the drug to make Tessa believe that he was getting better. Jem fell extremely ill, and there was no more yin fen for him, due to Mortmain stealing it all; Mortmain blackmailed Tessa into doing her binding until she did what he wanted: transformed in John Thadeus Shade. … 展开

At last, 129 years after he was made into a Silent Brother, Jem was "cured" from his state, when the yin fen in him was burned away by the heavenly fire in Jace Herondale, whom he constantly looked after for being Will's descendant. Upon recovering, Jem was once again a mortal. The repressed emotions that did not bother him as a Silent Brother … 展开