The Moon Rock — Arthur J. Rees

A classic locked room mystery from the genre's Golden Age by the renowned Australian author of the Chief Inspector Luckraft series.
 
On the day of his wife's funeral, Robert Turold reveals that he has completed his lifelong quest to prove his family's noble blood and restore its barony title. His brother and nephew will be his heirs, skipping over his daughter who he believes is illegitimate due to a deathbed confession from his wife. With the granting of a peerage within his reach, Robert has no qualms involving the neglected girl in public scandal -- a turn of events that has left the surviving members of his family reeling.
 
High on the Cornish cliffs, Robert's isolated and imposing Flint House proves the perfect backdrop for a mysterious crime, when he's found shot in a locked room. While first impressions point to suicide, Robert's sister is convinced he was murdered. Arriving from Scotland Yard, Detective Barrant suspects Robert's now-missing daughter, who has fled to London.
 
Mired in past secrets and sins, the case seems to go nowhere and everywhere at once. But the threads of obsession, greed, and revenge will lead to a devious killer, who is soon to be trapped in a web of their own design.