This discovery, strange as it was, seemed at first sight far enough removed from the circumstances of the murder, except so far as it brought the thought of lethal weapons to the imagination. But a weapon which required a percussion cap for its discharge had nothing to do with Violet Heredith's death. She had been killed by a bullet which fitted Nepcote's revolver, which was a pinfire weapon. The medical evidence had established that fact beyond the shadow of a doubt. Moreover, the percussion cap was unexploded, which seemed to make its presence in the grate even more difficult of explanation. It looked as though it had been dropped accidentally, but how came it to be there at all? The strangeness of the discovery was intensified by the knowledge that percussion caps and muzzle-loading weapons had become antiquated with the advent of the breech-loader. Who used such things nowadays? By the prompting of that mysterious association of ideas which is called memory, Colwyn was reminded of his earlier visit to the gun-room downstairs, and Musard's statement about the famous pair of pistols in the brass-bound mahogany box, which "carried as true as a rifle up to fifty yards, but had a heavy recoil." They belonged to the period between breech-loaders and the ancient flint-locks, and were probably muzzle-loaders. With that sudden recollection, Colwyn also recalled that Musard had been unable to show him the pistols because the key of the case had been mislaid or lost. This incident, insignificant as it had appeared at the time, seemed hardly to gain in importance when considered in conjunction with the discovery of the cap in the grate. Apart from the stimulus to memory the percussion cap had produced, there was no visible co-ordination between the two facts, because it was, apparently, quite certain that Mrs. Heredith had been shot by Nepcote's revolver, and by no other weapon. But the balance of probabilities in crime are sometimes turned by apparently irrelevant trifles which assume importance on investigation. Was it possible that the key of the pistol-case had been deliberately concealed because the box had something to hide which formed a connection between the pistols and the presence of the cap in the grate? That inference could only be tested by an examination of the case of pistols. The experiment was undoubtedly worth trying. Colwyn left the room and descended the stairs. CHAPTER XXVII