Jack Hammer was once a human, possibly a magic-user, who had held on to one too many secrets and became a gargoyle. At some point, he came to join the Library of Secrets and was assigned to watch Tim Hunter and Molly O'Reilly. Gargoyles were meant only to observe and report to the Library but never to involve themselves or interfere with the lives of those they watch. One night, however, Jack overheard Molly make a call in a phone booth to her father asking to come home and decided that Tim and Molly had to share their secrets and either come together or separate knowing the truth. Either way, this was meant to keep them from suffering the same fate as himself. Jack made himself known to Tim and Molly and shared secrets of each one cheating on the other and of Tim not paying attention to Molly ever since her return from Faerie. Molly felt their relationship couldn't be resolved and left. Before Jack Hammer left to face his fate for getting involved, he advised Tim of what gargoyles really are.