Statistics

The girl smiled and blushed. 'I'm ready', she said simply. Then, as she moved towards the door, she turned back. 'You said you knew I was not Lady Esther Carr before you saw me. How could you possibly tell that? 'Statistics,' said Mr Parker Pyne. 'Statistics?' 'Yes. Both Lord and Lady Micheldever had blue eyes. When the consul mentioned that their daughter had flashing dark eyes I knew there was something wrong. Brown-eyed people may produce a blue-eyed child, but not the other way about. A scientific fact, I assure you.'

The House at Shiraz
Parker Pyne Investigates
Agatha Christie (1934)
HarperCollins