The Murder of Roger Ackroyd: Agatha Christie

`Key is in the lock all right, sir. On the inside. Mr Ackroyd must have locked himself in.`
Poor Roger Ackroyd. He knew that the woman he loved had been harbouring a guilty secret - she poisoned her first husband. And yesterday she killed herself.
But guilty secrets rarely stay secret. Who had been blackmailing her before her death? Had it really driven her to suicide? And would it all be revealed in the letter that arrived in the evening post? Sadly Roger Ackroyd wasn`t going to live long enough to find out...