Gertie

In the short story The Veiled Lady, Gertie was a member of a gang of jewel thieves well known to Scotland Yard. She and her gang had robbed a shop of jewels in Bond Street but had been double crossed by a person named Lavington. Some members of her gang followed Lavington to Holland and murdered him but failed to recover the jewels as he had hidden them in his house. Gertie's gang then made two break ins into the house but also failed.

Finally, Gertie impersonated Lady Millicent Castle Vaughan and approached Hercule Poirot, with a story of her being blackmailed by Lavington, and persuading him to search for the letter in his house. Her gang knew the jewels would be in the same hiding place as the letter. Poirot saw through this because Gertie had worn scruffy shoes, something which, in his estimation, a high born lady would never do.

Portrayals
Gertie was played by Frances Barber in the film adaptation of The Veiled Lady in Series 2 of ITV's Agatha Christie's Poirot. There, Japp told Poirot that Gertie was the leader of the best "tomfoolery" (jewel theft) gang in the country.

After being arrested by Japp, Gertie explained how Lavington had gotten involved in her jewel theft operation, thus tying up a loose end which was not adequately explained in the original story. According to Gertie, Lavington had found out about the jewelers from one of his blackmail victims. He then gave Gertie the idea of conducting the robbery and insisted on having a part in it. Lavington was supposed to meet the rest of the gang members in his house to divide the loot but he never showed up. Gertie had seen the box where Lavington had hidden the blackmail letter and so guessed the jewels might be there also. As such, she decided to call on Hercule Poirot.