Marian and her sister Laura live a quiet life under their uncle's guardianship until Laura's marriage to Sir Percival Glyde, who is a man of many secrets. Could he be connected to the strange appearances of a young woman dressed all in white? And what does his charismatic friend, Count Fosco--whose white pet mice enjoy running in and out of his waistcoat--have to do with it all? Marian and the girls' drawing master, Walter, must turn detective in order to uncover the truth and to protect Laura from a fatal plot.