Gideon was originally a stray that found its way into Ramona's life, but then became Scott's when she disappeared. Gideon runs off at the end of Book 5, but returns months later to Scott in Book 6 when he's in his new apartment and trying to get his life back together. Scott accepts the cat's return since it's the only thing he has that connects him to Ramona while she is gone. The night the cat returns is the first night Scott sleeps soundly since Ramona's abrupt disappearance. (He had been haunted by nightmares of Ramona, Gideon, and other aspects of his girl troubles since her disappearance.)