One day, Lark and her friend Shelley, visit their neighbour, Ms Trowper, to fetch their ball from her garden. Ms Trowper is not her usual cheery self. She has a pool of water in her attic. She is convinced it is some kind of magic portal. She wants Lark and Shelley to see what's in it. The girls decide Ms Trowper is bonkers and make a hasty retreat. Later that night, Lark's mum insists she saw Lark's brother, Fin, and his 'sensible'...