"After you had signed the second time, what did Mr Marsh do? Do you know?"

"Went out to the village to pay tradesmen's books."

That did not seem very promising. Poirot tried another tack. He held out the key of the desk.

"Is that your master's writing?"

I may have imagined it, but I fancied that a moment or two elapsed before Baker replied: "Yes, sir, it is."

"He's lying," I thought. "But why?"

"Has your master let the house? - have there been any strangers in it during the last three years?"

"No, sir."

"No visitors?"

"Only Miss Violet."

"No strangers of any kind been inside this room?"

"No, sir."

"You forget the workmen, Jim," his wife reminded him.

"Workmen?" Poirot wheeled round on her. "What workmen?" The woman explained that about two years and a half ago workmen had been in the house to do certain repairs. She was quite vague as to what the repairs were. Her view seemed to be that the whole thing was a fad of her master's and quite unnecessary. Part of the time the workmen had been in the study; but what they had done there she could not say, as her master had not let either of them into the room whilst the work was in progress. Unfortunately, they could not remember the name of the firm employed, beyond the fact that it was a Plymouth one.

"We progress, Hastings," said Poirot, rubbing his hands as the Bakers left the room. "Clearly he made a second will and then had workmen from Plymouth in to make a suitable hiding-place. Instead of wasting time taking up the floor and tapping the walls, we will go to Plymouth." With a little trouble, we were able to get the information we wanted. After one or two essays, we found the firm employed by Mr Marsh.

Their employees had all been with them many years, and it was easy to find the two men who had worked under Mr Marsh's orders. They remembered the job perfectly. Amongst various other minor jobs, they had taken up one of the bricks of the old-fashioned fireplace, made a cavity beneath, and so cut the brick that it was impossible to see the join. By pressing on the second brick from the end, the whole thing was raised. It had been quite a complicated piece of work, and the old gentleman had been very fussy about it. Our informant was a man called Coghan, a big, gaunt man with a grizzled mustache. He seemed an intelligent fellow.

We returned to Crabtree Manor in high spirits, and, locking the study door, proceeded to put our newly acquired knowledge into effect. It was impossible to see any sign on the bricks, but when we pressed in the manner indicated, a deep cavity was at once disclosed. Eagerly Poirot plunged in his hand. Suddenly his face fell from complacent elation to consternation. All he held was a charred fragment of stiff paper. But for it, the cavity was empty.