Clara Button loves hats - making them and wearing them! But her favourite hat is the one that once belonged to her Granny Elsie. When her older brother Ollie breaks Granny Elsie's hat, Mum takes them on a special hat day out to cheer Clara up. While visiting the Victoria and Albert Museum, Clara gets lost and embarks on an exciting journey of discovery. Meanwhile, Ollie is having adventures of his own, with swords and tigers!.