Four days previously, Professor James McMurray of Gorling, in Essex, had been found dead in his laboratory, his head fearfully battered in by some blunt instrument.
It was the professor's custom, when engaged upon important research work, to retire, sometimes for days at a time, to a laboratory he had built in his own grounds.
Meals were passed through a small wicket, specially constructed for that purpose in the laboratory wall, and the professor's servants had the most explicit instructions on no account to disturb him.
A fortnight previously Professor McMurray had retired to his laboratory to carry out an important series of experiments. He informed his butler that Sir Jasper Chambers, his life-long friend, would visit him on the third day, and that dinner for two was to be supplied in the usual way, through the wicket.
On the evening in question, Sir Jasper Chambers had arrived and stayed until a little past nine. He then left the laboratory and proceeded to the house, where he told the butler that his master was quite well, and that in all probability his researches would occupy him another week.
Eight days later, when the butler took the professor's luncheon down to the laboratory, he noticed that the breakfast-tray had not been removed from the shelf just inside the wicket. Convinced that the professor had been so absorbed in his researches that he had forgotten the meal, the butler placed the luncheon-tray beside that containing the breakfast, thinking it better to leave the earlier meal as a reminder to the professor of his forgetfulness.
At dinner-time the butler was greatly surprised to find that both breakfast and luncheon had remained as he had left them; still, remembering how definite and insistent the professor had been that he was not to be disturbed, the butler had, after consulting with the housekeeper, decided to do nothing for the moment, and contented himself with ringing several times the electric-bell that was the signal of another meal.
An hour later he went once more to the wicket, only to discover that nothing had been touched. Hurrying back to the house with all speed he had conferred with Mrs. Graham, the housekeeper, and, on her insistence, he had telephoned to the police.
Sergeant Crudden of the Essex County Constabulary immediately bicycled over to "The Hollows," Professor McMurray's residence, and, after hearing the butler's story, he had decided to force the door; there are no windows, the laboratory being lighted from above, in order to secure entire privacy.
To the officer's surprise the door yielded readily, having apparently been previously forced. Entering the laboratory he was horrified to discover the body of the professor lying in the centre of the floor, his head literally smashed by a terrible blow that had obviously been delivered from behind.