Lady Millicent Castle Vaughan

In the short story The Veiled Lady, Lady Millicent Castle Vaughan approached Hercule Poirot and asked for his help in dealing with a blackmailer, one Mr Lavington. He had obtained an indiscreet love letter which she had written many years before and he threatened to show it to her prospective husband unless she paid over a vast sum of money.

Lady Millicent was the fifth daughter of a impoverished Irish peer and was engaged to marry the Duke of Southshire. Later Poirot would discover that the woman he met was not Lady Millicent at all. She had been impersonated by Gertie, a member of a gang of jewel thieves. The blackmail letter was also probably bogus.

Portrayals
Lady Millicent was also featured in the film adaptation of The Veiled Lady in Series 2 of ITV's Agatha Christie's Poirot. But, as in the original story, we only see her being impersonated by Gertie. Her father is however identified as the Earl of Killarney.