Mahou Senki Lyrical Nanoha Force. The plot seems to be based on investigating the Book of the Silver Cross, an ancient magical Belkan tome. While traveling, Thoma Avenir discovers a girl named Lily Strosek trapped inside a house. She gives Thoma an amulet when rescuing her which gives him access to a new Device power. Unknown to them, though, there is another one with a similar system that causes significant harm and injury, leading to a Time Space Administration Bureau investigation.