In other circumstances, Anstruther would have been pleased with the turn of events. He knew now that Smith, whom for so long he had been persecuting, was the rich Lord Barmouth. This, too, saved a deal of trouble; for instance, Serena need not have been brought here at all. Now Anstruther would be able to blackmail Barmouth for thousands, whereas he had been content with hundreds from the more humble Smith. Barmouth smiled, as he followed Anstruther's train of thought. He was reading the other's mind like an open book.

"I know exactly what you are thinking about," he said. "You are not sighing for lost opportunities; you are going to make it all up in the future. Still, I have puzzled you and, perhaps, frightened you a little. You are perfectly well aware why I have concealed my identity for so long. And you would give a great deal to know why I have so suddenly come out and met you in the open. On that point I have no intention of gratifying your curiosity. You may put your mask on again, and I will resume mine; but of one thing you may be certain. Either as Lord Barmouth or as James Smith, not one farthing more will you ever receive from me."

Barmouth turned contemptuously away, and unlocked the door.

"Now you can go your way, and I will go mine," he said. "I shall say nothing of this to Lady Barmouth; at least, not for the present. Make the best of your evening's pleasure. It will be the last time you will ever be under my roof.

"With an irritated feeling of defeat Anstruther stalked from the room, followed by Lord Barmouth, who lost no chance of hunting up Jack and Rigby. He told his interested listeners what had happened.

"I think you have acted wisely, Lord Barmouth," Rigby said. "We are so hot upon the track of Anstruther now that a day or two makes little difference. At the same time, I cannot quite see why Anstruther should have come here in this mysterious way, when he might have accompanied Claire quite openly."

Jack was inspired with a sudden idea.

"It's all a question of alibi," he said. "We know perfectly well what an ingenious scheme Anstruther has put up so that he may be what an Irishman would call in two places at the same time. Here is a magnificent opportunity of getting to the bottom of that mysterious music business."

"Right you are," Rigby cried. "It would be like flying in the face of Providence to throw away such a chance. Anstruther is here, and likely to remain, and so is Serena. You may depend upon it that the other maid has gone to bed, so that we should have the house in Panton Square all to ourselves. You know the ropes better than I do, Jack. Can you tell us a good way of getting into the house without playing the burglar?"

Jack thought a moment, then an inspiration came to him again; the thing was quite simple.

"We can walk into the place as if it belonged to us," he said. "When Claire came away, Anstruther told her that he should retire early. Claire did not wish to keep the servants up unduly, so she took a latch-key with her."

"Absolutely made for us," Rigby exclaimed. "You go off to Miss Helmsley and borrow her latch-key, and we will get to the bottom of the whole mystery whilst Anstruther is enjoying himself here."

Jack came back presently with the latch-key in his possession. It was an easy matter to get out of the house without being observed; then a cab was called, and the two proceeded to Jack's chambers, where they stripped off their fancy dresses hastily and assumed more civilized attire.

"I vote we take Bates into this business," Rigby suggested. "I've got a little idea of my own, which I will tell you about after we have been to Panton Square."

Unfortunately the services of Inspector Bates were not available, for he had been called out on some business of importance, and was not expected back till the following morning.

"We shall have to go through it ourselves," Jack said. "You will have a fine lot of copy for the Planet a bit later on. I declare I am getting quite fascinated by my present occupation. Shall we take a cab, or would it not be more safe for us to walk?"

Panton Square was reached at length, and No. 5 appeared to be in total darkness. As the friends had anticipated, Serena's fellow servant had gone to bed, for neither at the front or back of the house was there so much as a glimmer of light to be seen. An application of the latch-key to the door proved quite successful, and a minute later the two friends were inside. They had not the slightest hesitation in putting up the lights, so that the passing police might infer that the occupants of the place had returned. Not that he wanted to trouble much about anything but the study, seeing that it was there that the mysterious music always emanated.

It was an ordinary-looking room enough, the walls being entirely lined with books. There were books everywhere, not an inch of space being available for more. The ceiling was quite plain, and the closest search failed to disclose anything in the way of an apparatus by which the sounds of music could be conveyed from a distance into the study. Jack looked round with a puzzled frown.

"All the same, it must come that way," he said. "I know perfectly well that one of Padini's recitals came into this room as if it had been carried by some electrical means."

"A sort of telephone, I suppose," Rigby said. "Of course, we have all heard of the theatre-phone, but that theory would not work out in this case. With the dodge in question you have to plug both ears with a kind of receiver, and even then the music is only audible to those using the little receivers. In the present instance I understand that the whole room is flooded with melody, just as if the player were actually here."

"You've got it exactly," Jack explained. "I have heard it myself, and so has Claire; and both of us spotted the music as being in precisely the style of Padini. Hang me if I can see the slightest sign of how the thing is worked."

Rigby said nothing; indeed, he was hardly listening. He was pacing round the room pulling armfuls of books out here and there, as if expecting to find some cunning device hidden behind the volumes. He stooped to pick up Anstruther's violin case, which lay upon the floor. The case had been recently dropped, or some weight had fallen upon it, for the lid was cracked all across, and the hinges were broken. Rigby gave a little cry as he threw back the lid.

"Here's a discovery for you," he exclaimed. "Anstruther's violin with the neck broken off. If you will look at it closely, you will see that it is covered with dust, and evidently has not been used for days. Of co............