Caul is a Lost Boy who appears in the books Predator's Gold and Infernal Devices. In Predator's Gold, he can be mentioned looking at Tom Natsworthy and wondering why he is doing what he is doing. He eventually helps Tom and Hester, and as a punishment gets hanged, however is not killed, being saved by Gargle, a fellow Lost Boy.

He later settled in Anchorage-in-Vineland and married Freya Rasmussen.