...it is only when a man goes out into the world with the thought that there are heroisms all round him, and with the desire all alive in his heart to follow any which may come within sight of him, that he breaks away... from the life he knows, and ventures forth into the wonderful mystic twilight land where lie the great adventures and the great rewards.

He had maintained a platonic relationship with Jean while his first wife was still alive out of loyalty to her. A sequel to A Study in Scarlet was commissioned and The Sign of the Four appeared in Lippincott's Magazine in February 1890 under agreement with the Ward Lock company. Conan Doyle fathered five children.

He was a prolific writer whose other works include fantasy and science fiction stories plays romances poetry non-fiction and historical novels.