What Moves the Dead

What they find there is a nightmare of fungal growths and possessed wildlife, surrounding a dark, pulsing lake. Madeline sleepwalks and speaks in strange voices at night, and her brother Roderick is consumed with a mysterious malady of the nerves. Aided by a redoubtable British mycologist and a baffled American doctor, Alex must unravel the secret of the House of Usher before it consumes them all.