In the novel The Body in the Library, Conway Jefferson is the wealthy head of the Jefferson family. He is a widower; his wife Margaret and children Frank and Rosamund had all died in an aircrash some time before the events in the novel. Conway himself had both legs amputated and was left wheelchair-bound after the accident. Conway is an old friend of Colonel and Mrs Bantry, as well as Sir Henry Clithering.
Conway has red hair, which is slightly grizzled. His face is "rugged and powerful, deeply sun-tanned", and his eyes are "a startling blue". He is a strong personality, and gives the impression that "The injuries which had left him a cripple had resulted in concentrating the vitality of his shattered body into a narrower and more intense focus".
He has a heart condition, and Dr Metcalf had warned that he was not to be over-excited or startled.
Conway says that when he lost his wife and children, it was as if he had lost half of himself, because he was a family man. His son-in-law, Mark Gaskell, and daughter-in-law, Adelaide Jefferson, were good to him, but he realised that they had their own lives to live. He was lonely, and thought of adopting a boy or girl.
During the month before the events of the novel, he met Ruby Keene at the Majestic Hotel, and grew fond of her. He decided to adopt her legally, and about ten days before the events of the novel, made a new will leaving fifty thousand pounds in trust for her until she turned twenty-five, when she would come into the principal.
On the night of Ruby's disappearance, Conway plays bridge with Josie Turner, Mark, and Adelaide. When Ruby is still missing the next morning, and her room has not been slept in, he insists on notifying the police. When she is discovered dead, he asks Sir Henry Clithering to come and investigate.
Towards the end of the novel, Conway tells Mark and Adelaide that he intends to make a new will, leaving the money that would have gone to Ruby, to endow a hostel for young dancers in London. This is part of a plan by Miss Marple, to be sure of the identity of the murderer. That night, the murderer enters Conway's room, and attempts to kill him with an injection of digitalin, but is caught in the act by the police.