In the novel Sparkling Cyanide, Ruth Lessing is the highly efficient secretary of George Barton, who considers her his right hand. Ruth was considered a member of the family and was frequently invited to the Bartons’ Elvaston Square house. During the evemts of the novel, Ruth is twenty-nine, but she had not changed from since she was twenty-three years old. Ruth would have wanted to marry George Barton despite he was already married, and thus had a motive for killing Barton’s wife Rosemary.
A week before the death of Mrs Barton, George Barton asked Ruth to visit Victor Drake.
Ruth Lessing falls for Victor, and schemes and murders to gain the inherited wealth by killing all those in the list before Victor. She poisoned Rosemary Barton, and tried to kill Rosemary’s sister three times. If she died, the money would have passed to Lucilla Drake, Victor’s mother. Victor would have inherited indirectly because he always managed to obtain financial aid from his mother. However, George Barton died in the place of the intended victim Iris.
Agatha Christie used the name Ruth Lessing as a pun for a ruthless female conspirator.