Mary Aldin

In the novel Towards Zero, Mary Aldin is the companion of Lady Tressilian, whom she is a distant cousin of. She came to work for Lady Tressilian after her father died. At the time of the events in the book, she is 36 years of age and had been with Lady Tressilian for some 15 years. To Thomas Royde she presents a picture of one who is "Calm, tactful, an excellent manager." She has had a natural lock of white in her hair since she was a child.

Audrey Strange though Mary must have found her life very restrictive, always at Lady Tressilian's beck and call, managing the servants and never having a chance to go away. However Mary considered her life fortunate, as she was well-fed and house. And she also managed to have her own private distractions. This comprised trying small psychological experiments on people, to see if she could make them react to what she said in the way she intended. However the rest of the plot does not really develop this.

At the end of the book, there is a suggestion that Mary would pair off with Thomas Royde. Audrey Strange says that Thomas Royde really cares for her "but doesn't know it yet".

Agatha Christie's Marple
In the 2007 ITV adaptation of the story. Mary Aldin is portrayed by Julie Graham. The portrayal is fairly faithful to the original and depicts much about her management skills with regards to people and household matters. There is also some development of a relationship between her and Thomas Royde. However, because Angus MacWhirter is not featured in this adaptation, Thomas is the one who pairs off with Audrey Strange in the end.