The man bowed and smiled to the lady, and she bowed and smiled in return. It was rather a graceful bow; it seemed to Jack that she looked at her companion to see if it were quite correct. Then the two proceeded to talk in dumb show, partly by signs and partly by fingers. The mystery was getting deeper--one of these two was a deaf mute, perhaps both of them. Was this one of Anstruther's cases, or did it possess a far deeper significance?

The solution was beyond Jack Masefield. He might have been on the track of a mystery, and on the other hand he might merely be doing a little vulgar eavesdropping. If it was the latter, and Anstruther found him out, he need not hope to visit Claire at home any more. Anstruther was most particular about these things, as Jack knew; but he set his teeth together and decided to take the risk. He felt pretty sure that there was something here that touched the household deeply.

He turned just for the moment, with an idea that somebody was behind him. But the strip of lawn was quite clear. Jack could see through the belt of trees to the street again beyond, with its great arc light flaring on the yellow face of the mysterious Nostalgo and his starting, half-laughing eyes. That weird face seemed to form a fitting background to the room mystery.

But Jack had his eyes to the slit in the blind again. Inside the pantomime in show was still going on. The girl seemed to be getting a lesson of some kind, and her tutor appeared to be pleased, for he smiled and clapped his hands from time to time. Then he took out his watch and consulted it with a frown. As he glanced up the girl crossed the room to the mantelpiece and opened the face of the clock. With a quick movement she put it back half-an-hour.

The man in the faultless evening dress nodded approval. There was a little pause before he approached the window and stood so that his shadow was picked out clean against the strong light of the room. Then he rapidly signaled with his arm. One arm went up, there was a noise of rings and a flutter of drapery, and then a heavy curtain was jerked over the window, and Jack could see no more. Try as he would, no ray of light could he make out. It was as if the lights had been switched off, leaving the room in utter darkness.

What on earth did it all mean? Beyond doubt the young man in evening dress had signaled to somebody outside when he stood close against the window and raised his arm. Jack congratulated himself on the fact that the slit in the blind was low down, so that he had not to stand against the light. He slipped into the belt of shrubs and watched for a moment, but no further sign came.

What were those people inside going to do? The solution flashed upon Jack instantly. They had not come there so perfectly dressed for the mere sake of seeing Spencer Anstruther. They had not been spending the evening anywhere, dining and that kind of thing beforehand, for they looked too spruce and fresh for that. The woman's toilette in particular had evidently been just donned, as if fresh from the hands of her maid. And she had put the clock back half-an-hour.

"They are going somewhere in half-an-hour," Jack decided. "Hang me if I don't follow them. By the right time it is half-past ten. Anstruther said he should not come up if he failed to get his business finished before eleven, at which time he will expect me to go. I'll go up to the drawing-room and talk to Claire for a little time just to avert suspicion."

He crept back into the house without being seen, he finished his claret, and dropped the stump of his cigarette on to his dessert plate. As he made his way up the stairs the music began again. That music was not the least maddening part of the mystery.

"What a time you have been," Claire said as she tossed her book aside. "All by yourself down there! Really, Jack, you modern young men are so cold-blooded that----"