The White Room by Fergus Hume

Mulligan stared at the dead woman, but beyond touching her to see if life remained, he did not attempt to alter the position of the corpse. For corpse it was. The woman was as dead as a stone, and Mulligan knew his duty too well to take any authority upon himself The inspector was the man to issue orders, and the inspector would be at the head of Achilles Avenue when the clock struck twelve. As this thought passed slowly through the policeman's mind -- for the unexpectedness of the tragedy had somewhat dazed him -- he heard the midnight chimes. With a sudden start he recovered his wits and wheeled round. In a few minutes he was out of the house, and had closed the door. Only when in the roadway did his brain begin to work at its normal speed.

"It's that young gentleman," thought Mulligan. "He said I'd come across a crime sooner than I expected. And the key is his. Mary, be good to us; but he must have killed the poor creature before he joined me. Augh! " He stopped and considered. "But if that's so, what about the singing. She was at the piano, and the song wasn't done when the gentleman joined me. Augh!"