Jacko Argyle is convicted of having killed his foster-mother. Two years later, he dies in prison while serving his sentence. After his death, a stranger, Arthur Calagry, turns up at the Argyle household claiming that Jacko was innocent and that on the fateful night of the murder, he had taken lift from Arthur. He hopes that the others would be happy to hear his testimony, what he doesn't realise is that now that the old wound is re-opened, it would bleed the rest of the family, as secrets come out in the open and every member is suspicious of the other.
This is one Agatha Christie that I didn't particularly enjoy. Don't know what put me off since the plot is gripping but somehow or the other, it failed to impress.
Entry for letter O in the Crime Fiction Alphabet meme.