The Dark Eyes of London by Edgar Wallace

Larry sat on the iron bedstead of the cell, his aching head between his hands. He had anticipated many ends to that night's adventure, but never did he imagine that he would be trapped like a rat, and that the mystery of Box A would be solved in so startling a fashion. So that was the explanation of Gordon Stuart's death. He had accepted the invitation of Dr Judd to go with him in his box, and there had met the sinister figure of Dearborn. He had either been drugged or clubbed to insensibility and had been carried in John Dearborn's strong arms through the emergency door in the passage and whisked away to the House of Death.

If he had not anticipated such an end to the evening, he thought, he had at least made some preparations. Instinctively he had known that of all places on the face of the earth where his quarry would be run down and 'Finis' might be written to the Stuart case, no other spot was so likely as in this terrible mansion which the Judds had built for themselves, and the object of his visit that morning had been twofold.