We’re done, Brother Zachariah said. Go from here and do not return.

“Absolutely!” Belial said. “Only, about that favor. It pains me so to be in debt to you when I might be of some service. I wonder if there isn’t a thing that I could offer you. For example, the yin fen in your blood. Do the Silent Brothers still not know what the cure might be?”

Brother Zachariah said nothing, but Sister Emilia could see how his knuckles grew white where his fist was clenched. At last he said, Go on.

“I might know a cure,” Belial said. “Yes, I think I know a sure cure. You could be who you once were. You could be Jem again. Or.”

Brother Zachariah said, Or?

Belial’s long tongue flicked out, as if he was tasting the air and found it delicious. “Or I could tell you a thing you don’t know. There are Herondales, not the ones you know, but of the same bloodline as your parabatai. They are in great danger, their lives hang by a thread, and they are closer to us as we stand here than you can imagine. I can tell you something of them and set you on the path to find them if that is what you choose. But you must choose. To aid them or else to be who you once were. To once more be the one who left behind those who loved him best. The one they still yearn for. You could be him again if that is what you choose. Choose, Brother Zachariah.”

Brother Zachariah hesitated for a long moment.

In the mirrors around them, Emilia saw visions of what Belial was promising, of all that his cure would mean. The woman Brother Zachariah adored would not be alone. He would be with her, able to share her pain and to love her wholly once more. He could rush to the side of the friend he loved, see his friend’s blue eyes shine like stars on a midsummer night as he beheld Brother Zachariah transformed. They could clasp hands with no shadow of grief or pain upon them, just once. They had been waiting all their lives for that moment, and feared it would never come.

In a hundred reflections, Brother Zachariah’s eyes flew open, blind and silver with agony. His face twisted as if he were being forced to endure the most terrible pain or, worse, forced to turn from the most perfect bliss.

The real Brother Zachariah’s eyes stayed closed. His face remained serene.

At last he said, The Carstairs owe a life debt to the Herondales. That is my choice.

Belial said, “Then here is what I will tell you about these lost Herondales. There is power in their blood, and there is great danger, too. They are in hiding from an enemy who is neither mortal nor demon. These pursuers are resourceful, and close on their heels, and they will kill them if they find them.”