The Cuckoo Tree Av Joan Aiken

While her friend Capt Hughes recovers from a carriage accident, Dido is marooned with the odd inhabitants of the Tegleaze estate. Soon suspicious things happen; a priceless possession is stolen, a boy kidnapped, a twin sister found and when Dido catches a glimpse of her rascally father in Petworth, she is sure she is in the midst of another wicked Hanoverian plot. Can she combat mass hypnotism, smugglers, and a gang of murderers to prevent the plot to put St Paul`s Cathedral in the River Thames?