Clotilde is described as a handsome, tall and well educated. She is seen as a great contrast to her plain sister Lavinia and her mad youngest sister Anthea. Miss Marple compares her to Clytemnestra, but she is too sweet to be a murderer.
Clotilde's early life is questionable due to her standing, she is clearly a smart person, but the staff are unable to agree if she went to University, it is suggested she did but was too poor to continue to be a scholar, or that she never went and looked after her older Mother then moved in with her sisters after her Uncle's death left them with the Old Manor House and finance security.
She was a close friend of Verity Hunt's mother and adopted the girl after the death of her parents. After she finished Clotilde took Verity on several trips to Europe and planned a great future for her, she wasn't happy when she found that Verity had fallen in love with Michael Rafiel. After Verity was murdered Clotilde had to identify the body and was never the same afterwards, refusing to repair the Greenhouse which she and Verity loved and the house fell silence.
When Jason Rafiel died, the sisters welcomed Miss Marple as was his wish when she came on the coach tour especially with the harder visits. During that time Marple slowly found the truth when she revealed Verity's name Clotilde broke down. While at dinner with the sisters and Miss Barrow and Miss Cooke, Miss Marple explained why she was here and her theory. Clotilde offers her a coffee but Cooke suggests Warm Milk instead.
At 3 am Clotilde entered Miss Marple's room and she was there ready to confront her with the truth. She poisoned Verity Hunt, to stop her from running off with Michael Rafiel, she also buried Verity in the site of the old greenhouse and she killed Nora Broad to identify her as Verity. Since Elizabeth Temple also realised this Clotilde went to the hike in disguise and killed her with the boulder.
Clotilde goes to kill Marple only for her to whistle so Messes Barrow and Cooke appeared with guns. After Marple is protected, Clotilde took her own life with the Milk she poisoned earlier. After this is revealed Marple discovers that Temple contracted her to help her confess and the disguise Clotilde sent as a package to a charity.
In the 1987 BBC version, Clotilde was played by Margaret Tyzack, this adaption was mostly faithful to the story save for the change that Clotilde dropped a Bust on Miss Temple in the Drawing Room of Kingmister Castle. Also she is found dead in the ruined Greenhouse where Miss Marple explains to her grief stricken sisters that Verity is buried there.