When Maisie Brown is time-shifted to 1471 during a school trip to Warwick Castle, it's the beginning of an adventure bigger than she could ever have dreamed of. The only problem is she has to share it with Lizzie Andrews, the class bully, instead of her best friend Danny Romano, who has managed to get caught up amongst the Earl of Warwick's army marching towards the Battle of Barnet. Determined to save Danny, Maisie and Lizzie leave the safety of the castle and follow after the army. Battling against everything that Medieval England throws at them, the girls find unexpected help from a Lord with a surprising secret, and discover that two mysterious hooded riders are trying to hunt them down. With time fast running out to find Danny they begin to realise that they have the unlikeliest of allies looking out for them.