The Pit-Prop Syndicate by Freeman Wills Crofts

Almost exactly fifteen hours before Merriman's call at Scotland Yard, to wit, about eight o'clock on the previous evening, Inspector Willis of the Criminal Investigation Department was smoking in the sitting-room of his tiny house in Brixton. George Willis was a tall, somewhat burly man of five-and-forty, with heavy, clean-shaven, expressionless features which would have made his face almost stupid, had it not been redeemed by a pair of the keenest of blue eyes. He was what is commonly known as a safe man, not exactly brilliant, but plodding and tenacious to an extraordinary degree. His forte was slight clues, and he possessed that infinite capacity for taking pains which made his following up of them approximate to genius. In short, though a trifle slow, he was already looked on as one of the most efficient and reliable inspectors of the Yard.

He had had a heavy day, and it was with a sigh of relief that he picked up the evening paper and stretched himself luxuriously in his easy-chair. But he was not destined to enjoy a long rest. Hardly had he settled himself to his satisfaction when the telephone bell rang. He was wanted back at the Yard immediately.