Adele was very beautiful, and had blue eyes with a "shrewd appraising quality". In figure and type, she resembled Irene Grosvenor, but Miss Grosvenor is glamour without and respectability within, while Adele was glamour all through. She was about thirty years younger than her husband.
Adele and Rex met at Brighton, where she had been working as a manicurist. She married him for his money, according to Mary Dove.
Adele and Vivian Dubois were lovers, and often played golf or tennis together. About five weeks before the events of the novel, Adele made a will leaving everything to Vivian.
According to Rex Fortescue's will, Adele was to inherit a hundred thousand pounds when he died, if she survived him for at least one month. However, because she did not survive him for one month, she did not inherit the money.
Adele was found dead in the drawing room at Yewtree Lodge after tea, the day after Rex died. The cause of death was poisoning by cyanide, which had been in her tea.
In the ITV 2008 adaptation of the novel (Episode 1, Season 4 of Agatha Christie's Marple), the part of Adele Fortescue is played by Anna Maddeley.