Septimus Grimpton passed a shaky hand across his brow.
"That is perfectly correct, Mr Pons. I had not seen the connection."
"There is no reason why you should have, Mr Grimpton. And you would certainly not have suspected your own brother of any ill will."
"If I had known of his intentions, Mr Pons, I would gladly have shared my grandfather's treasure with him." Solar Pons smiled wryly.
"Ah, there we have one of the supreme ironies of life, Mr Grimpton. Two men lying dead and all these tragic circumstances, with greed again responsible. Now, from what Inspector Morgan tells me and from what I have been able to piece together, it is almost certain that the man Stokoe and your brother together plotted to steal the secret cache of valuables from the Mausoleum. Your grandfather's eccentricity had devised, as he thought, a perfect way of guarding his valuables. He had constructed the secret room beneath the sarcophagus of his wife, telling everyone at the time that he himself would be interred there. This was the reason the plinth pivoted on that curious turn-table. I had seen the circular groove in the floor when we visited the building but foolishly failed to make the connection, taking it to be part of the pattern of the tiling. It was cunningly done, so there may be some slight mitigation in my own defence.
"Of course, it was obvious to me at once that the quarrel and the knife theory regarding the gypsy would not hold water. It was evident from the circumstances that the fatal blow had been struck within the Mausoleum. But there was the problem of the missing weapon; and furthermore, there was no trace within the chamber of the man who had struck the blow. I saw these facts at once and also noted the curious corollary that the old gentleman himself was interred on the far side of the Mausoleum, away from his wife. But I had not then learned of the story of the treasure from Mr Grimpton, neither did anyone know anything about the hidden chamber, so that I was unable at that time to piece these disparate segments together."
"Come, Pons," I said. "You are being too modest."
Solar Pons made a faint clicking noise with his tongue.
"I should have seen the connection at once, Parker. The fact that the grandfather was interred on the far side should have plainly spelled it out to me. He left careful instructions in his will about that, I now understand. And to guard the valuables he left the terrible device, so picturesquely referred to by the unfortunate Stokoe, as The Shaft of Death. Perhaps you can enlighten us there, Mr Grimpton?"
"I cannot vouch for it, Mr Pons, but I often heard my father say that Grandfather was a wonderful mechanic and watch-maker. It was a particular hobby of his."
Solar Pons inclined his head with a sombre expression.
"He said nothing, of course, about this diabolical instrument in his estate book notes, so your brother would have had no inkling of the danger. And he naturally did not anticipate Stokoe's own treachery in attempting to secure the money for himself."
"I am still not clear about all this, Pons," I said.
"And yet it was all there before us, Parker," said Solar Pons. "I myself failed to draw the necessary conclusions until quite late in the day. The bloodied hand-prints Stokoe left on the tomb effigy were not simply put there when he tried to steady himself when dying. Gravely wounded as he was, his first instinct was to protect the secret by pushing the plinth back over the entrance passage. In so doing he used almost his last strength and he was undoubtedly on his way to the house either to warn or upbraid your brother when he collapsed and died, Mr Grimpton."
The old man shook his head.
"A terrible story, Mr Pons."
"The connection between Stokoe and the late Thaddeus Grimpton is by no means clear," said Inspector Morgan, clearing his throat.
"Yet, it was perfectly simple once we had learned the motive," said Pons. "Grimpton had the secret and he guessed, rightly, that a fortune lay within his grasp. But to remove the treasure he needed a man more used to danger and the sterner side of life. He was himself a scholar and a man well into late middle-age. He required a ruthless, younger man, who would work under his direction for a share of the fortune. He found that man in the person of the ex-convict, Abel Stokoe."
"I see, Pons," I said. "You mean…?"
"Exactly, Parker," Solar Pons interrupted cuttingly. "It leapt at me when Mr Grimpton here said his brother was a member of charitable trusts and a prison visitor. Bristol Gaol was the former habitation of Stokoe, and Grimpton visited there. He no doubt cultivated Stokoe over several years and primed and recruited him before his release. He would have been the perfect tool. Used to dangerous house-breaking work at night and physically strong, as he would need to be, to remove the materials Grimpton hoped to find in the vault. But the two men either quarrelled or else Stokoe decided, unknown to his employer, to make his own attempt on the Mausoleum.
"The doors had been greased so as to avoid attracting attention by making a noise at dead of night and Grimpton had stolen the key from Captain Mannering's desk at the estate office, after having found it impossible to get at either of the two keys Mr Granger kept in the study."
"They were away under lock and key, Mr Pons," said the secretary earnestly. "I made sure of that."
"So that was what you meant at the Home Farm, Pons," I said. "But how did Stokoe get the key?"
"But surreptitiously making a wax impression of the stolen one," said Pons. "We can be reasonably sure that this would have been done when the two men first vis- iced the Mausoleum to try to uncover its secret. They may well have made several nocturnal excursions for, as you have seen, Inspector, the catch which actuates the pivot is damnably hard to find."
"That is so, Mr Pons."
"You may remember, Parker, I particularly questioned Mr Granger about the keys and was reasonably satisfied that no-one could have had access to them. There remained then the only other known key, that at the Estate Office. When we visited Captain Mannering there, I saw at once that the key must be missing. He was so ill at ease and inclined to bluster that I was sure the key left in his charge had been stolen. He felt guilty and realised he might be implicated after the Mausoleum had been found open and Stokoe murdered. He was not going to admit to the key's loss without a struggle and nor do I blame him."
"Even so, Mr Pons…" our host began.
"What you decide about your Estate Manager is your business, Mr Grimpton," continued Pons. "I am merely stating the facts."
"But how would anyone have got the key?" I asked.
"Pshaw, Parker, use the evidence of your eyes. We were complete strangers when we arrived at Home Farm yet the groom immediately directed us to the Estate Office, which was empty. Any intruder would have only to search the desk undisturbed to find the key. And as Mr Thaddeus Grimpton was a trusted member of the household and might well have visited the Farm in the normal course of events, nothing would have been easier than to get hold of that key. I do not like telling tales out of school, Mr Grimpton, but it was common knowledge that the Captain liked the bottle and he might not have discovered the theft of the key for weeks. He only realised its significance following the tragic events at the Mausoleum and quite naturally attempted to cover things up when I so unexpectedly visited him."
"You make it sound so easy, Pons," I said.
Solar Pons shook his head.
"On the contrary, Parker, I have been extraordinarily obtuse. It is extremely difficult when working without discernible motive, as we were. And the gypsy Smith's action in throwing the knife into the river confused the issue."
"Do not remind me of that, Mr Pons," said Inspector Morgan ruefully.
"You acted perfectly correctly as an official representative of the law, Inspector. Stokoe had stayed at the caravans with Smith and his fellow gypsies. For the business he had on hand in the neighbourhood, it probably suited his purpose to submerge himself among the Romanies. And if anything had gone wrong they might well have been blamed. But he was a surly fellow, as we have learned, and he quarrelled with his gypsy hosts and was told to leave. This was awkward, as he was placed close to his base of operations at the estate. He could not stay at Penderel Parva because it was too small and might excite comment so he took cheap lodgings in Bath. There Inspector Morgan recovered the mould from which he made the fourth key to the Mausoleum entrance, the one found in the door. You have been extremely useful in that direction, Inspector."