“I wish everybody in Praed Street would deal with me as frankly as you have, Mr. Ludgrove,” replied Whyland. “There seems to be a sort of dread in the minds of most of them that the police will in some way take advantage of everything they say. Take Copperdock, for example. I’ve been talking to him, and he tells me he was at the Cambridge Arms for half an hour or so some time between one and two. Yet neither he nor his son will tell me exactly what time he left his shop or returned to it. They didn’t notice, they say.”

“ Mr. Copperdock is not blessed with a very exact mind,” said Mr. Ludgrove soothingly. “You remember the curious incident of his meeting with the black sailor some time ago. By the way, I suppose that rather intangible person has not yet appeared in connection with the present case, has he? Although nearly everybody whom I have seen this evening has some theory to account for the facts, I have so far heard no reference to the black sailor.”