Guardian of the Diamond Arrow, Flip Side 1

Joan Ilion is no stranger to dangerous situations, and she's made it her life's mission to step in when children are in danger. When she sees a child being kidnapped, she doesn't hesitate to throw herself in the middle. But things aren't exactly what they seem. These men are looking for a traitor that crossed through a portal to her world, what they call the Flip Side. No adult from the Flip Side has ever been through the portal to see their medieval world, but Joan has the unique ability to do just that. Caught between two worlds, Joan has a life already established, and a younger sister, that she's reluctant to leave. But there's a war going on that spells a dark end for the people Joan has come to know, and she may be the key to ending it.