When 13-year-old Amanda Sault and her annoying classmates are caught in a food fight at school, they're given a choice: suspension or yard duty. The decision is a no-brainer. Their two-week crash course in landscaping leads to the discovery of a weathered stone arch in the overgrown back yard. The arch isn't a forgotten lawn ornament but an ancient time portal from the lost continent of Atlantis.

Chosen by an Atlantean Magus to be Timekeepers—legendary time travelers sworn to keep history safe from the evil Belial—Amanda and her classmates are sent on an adventure of a lifetime. Can they find the young Robin Hood and his merry band of teens? If they don't, then history itself may be turned upside down.