Charlotte Grayson and her sister Kitty are living with their widowed mother at Westbury Hall, which they are renting from the wealthy Sir Benjamin Westbury. When he returns home unexpectedly, he brings with him his handsome great-nephew, Hugo, who demands that they leave the Hall forthwith. Then, during a violent thunderstorm, part of the library panelling is broken away, revealing a gruesome skeleton. The man has obviously been murdered, but who is he and how did he get there? As this gripping story unfolds, past family tensions are revealed and Charlotte puts herself in mortal danger.