Mr. Henry Bacon is a man that lives by Liz and Lucy. He is a librarian. According to Icefire, he had once been in the army. He loaned David books about the Arctic and even let him stay at his house for a little while. In Firestar, he invited Liz and David over for Christmas while Lucy was in the Arctic, and he serves a punch that makes Liz tipsy. His Grandfather went on an Arctic expedition in the 1900's.
Henry is the one who teaches David about "Doctor Bergstrom" and that he had gone on an Arctic expedition fifty years ago, which made David wonder about Bergstrom.
Henry vaguely knows Zanna, as she visits his library. Later in the books, he and Zanna established a relationship and he considers her as the daughter he never had.
Their bond was so close that when he "died" he gave his house to Zanna.