The Old Lag by R. Austin Freeman

The case which I am now about to describe has always appeared to me a singularly instructive one, as illustrating the value and importance of that fundamental rule in the carrying out of investigations which Thorndyke had laid down so emphatically -- the rule that all facts, in any way relating to a case, should be collected impartially and without reference to any theory, and each fact, no matter how trivial or apparently irrelevant, carefully studied. But I must not anticipate the remarks of my learned and talented friend on this subject which I have to chronicle anon; rather let me proceed to the case itself.

I had slept at our chambers in King's Bench Walk -- as I commonly did two or three nights a week -- and on coming down to the sitting-room, found Thorndyke's man, Polton, putting the last touches to the breakfast-table, while Thorndyke himself was poring over two photographs of fingerprints, of which he seemed to be taking elaborate measurements with a pair of hair-dividers. He greeted me with his quiet, genial smile and, laying down the dividers, took his seat at the breakfast-table.