Gladys Martin was a maid of Rex Fortescue at Yewtree Lodge. She had previously been a maid of Miss Jane Marple who trained her. When she died in the course of the events in the story, Miss Marple felt obliged to get involved.
Gladys was a orphan, from St Faith's Orphanage, who went into service for Miss Marple who despite Gladys' flaws was willing to give her a good reference, she was stout with a homely face and had the habit of getting nervous when she broke something and would say she didn't do it. Miss Marple also found her quite gullible and clumsy.
She then became a maid at Yewtree Lodge, the home of Millionaire Rex Fortescue, during this time the staff mocked her behind her back, she however during a holiday met a man called Albert Evans whom she fell in love and no doubt made sure she answered the Telephone in case it was him. After Rex was murdered with taxine she was interviewed by Inspector Neele, she acted in fear that he was accusing her claimed innocents. However she's cleared of any crime, but afterwards she is found dead strangled in the yard, with a clothes pin put on her nose following the nursery rhyme Sing a Song of Sixpence as Adele has also been killed.
Miss Marple goes up to Gladys' Room and finds evidence of her ward's life with a boyfriend named Albert Evans and uncovers the truth.
It turned out that Gladys had committed the killing of Rex Fortescue, but at the time, she didn't realise it. Her boyfriend Albert had convinced her that taxine was a truth drug and so she added it to the marmalade and placing the rye in Rex's pocket when she realised it she used her typical mistake defence, which Neele didn't guess was a confession and Albert met her in the garden where he strangled her. Her Albert was Lance Fortescue, who used her connections to his Father to get his hands on the Blackbird Mine. After Lance is arrested Miss Marple returns home finding a letter from Gladys confessing to the crime and a picture of her and Lance proving the evidence needed for the conviction.
- 1983 - In the 1983 Russian adaptation, Gladys is portrayed by actress Irina Mazurkevich
- 1985 - In the 1985 adaptation, part of the Miss Marple television series, Gladys is portrayed by actress Annette Badland.
- 2008 - In the 2008 adaptation, part of Agatha Christie's Marple, Gladys is portrayed by actress Rose Heiney.