The Master Mind of Mars by Edgar Rice Burroughs

It was usually about three hours after the evening meal, which was served immediately after dark, that the establishment quieted down definitely for the night. While I should have preferred waiting longer before undertaking that which I had in mind, I could not safely do so, since there was much to be accomplished before dawn. So it was that with the first indications that the occupants of the building in which my work was to be performed had retired for the night, I left my quarters and went directly to the laboratory, where, fortunately for my plans, the bodies of Gor Hajus, the assassin of Toonol, and 378‒J‒493811‒P both reposed. It was the work of a few minutes to carry them to adjoining tables, where I quickly strapped them securely against the possibility that one or both of them might not be willing to agree to the proposition I was about to make them, and thus force me to anesthetize them again. At last the incisions were made, the tubes attached and the motors started. 378‒J‒493811‒P, whom I shall hereafter call by his own name, Dar Tarus, was the first to open his eyes; but he had not regained full consciousness when Gor Hajus showed signs of life.

I waited until both appeared quite restored. Dar Tarus was eyeing me with growing recognition that brought a most venomous expression of hatred to his countenance. Gor Hajus was frankly puzzled. The last he remembered was the scene in the death chamber at the instant that his executioner had run a sword through his heart. It was I who broke the silence.