What Nanny Knew

A well known wealthy and landed family are murdered one by one until there is only one remaining.
The police are put under pressure to solve the cases before the last member is murdered. Time is short and with no success on the horizon. Jack the Hat a retired detective from New Scotland Yard is brought in by the chief Constable as an advisor.
He brings his expertise, reviews and advises officers, finally becoming involved himself.
A real exciting mystery to the very end.