Philemon Abernathy is the Head Librarian of the Gervaisius Estate and is seen in the T2 missions "Casing the Joint" and "Masks".
He was recently hired[1] to replace Giles, after this sudden disappearance, and Ashton, who resigned to take a higher paying job and to get away from 'painful memories'[2]
While filing some letter for Lord Gervaisius, he heard strange sounds and a whole book Stack disappeared. When reporting this 'haunting' to the house guards, they were somewhat less then helpful.[3]