Monsieur Lecoq by Emile Gaboriau

Lecoq did not sleep that night, although he had been on his feet for more than forty hours, and had scarcely paused either to eat or drink. Anxiety, hope, and even fatigue itself, had imparted to his body the fictitious strength of fever, and to his intellect the unhealthy acuteness which is so often the result of intense mental effort.

He no longer had to occupy himself with imaginary deductions, as in former times when in the employ of his patron, the astronomer. Once again did the fact prove stranger than fiction. Here was reality -- a terrible reality personified by the corpses of three victims lying on the marble slabs at the Morgue. Still, if the catastrophe itself was a patent fact, its motive, its surroundings, could only be conjectured. Who could tell what circumstances had preceded and paved the way for this tragical denouement?