The Care family, with Sir Henry Care at its head, is based at Naneslow, its decaying family estate in Cornwall. Sixteen years before, there was a death in the family when Deborah, Sir Henry's first wife, fell from the top of Naneslow's tower. Since re-married to Nancy, Sir Henry still has living with him his children from his first marriage, the twins Laura and Harold. Also living in the house are Isobel, Sir Henry's sister, and Celia, his cousin, with her daughter Alice. This is the cast of a Gothic mystery and psychological thriller.