Hanslet left the police station, more convinced than ever that the Professor was suffering from some temporary aberration. He had known such cases before, where overwork had caused the queerest effects. It was quite understandable. The Professor had certainly discovered the motive for the murders; it could not be a coincidence that all the men who had died had served on this particular jury and had been the victims of this mysterious murderer. But, having discovered this, and realizing that he was the only survivor, the Professor must have received a shock which had unduly stimulated his imagination. This was all that Hanslet could make of it. Meanwhile he determined to keep a very close watch over the Professor, for, if his theory was correct, his life was undoubtedly threatened, Black Sailor or no Black Sailor.

The party returned to London on the Monday morning, and Hanslet immediately went to see Whyland, whom he had left in charge during his absence. At the police station he was told that he had gone to see Mr. Ludgrove, and thither Hanslet followed him.