All of this, however, failed to explain the trouble Grantley had evidently taken to procure the note and check, and his strange action in subsequently destroying the latter.
He had laid himself open to suspicion by his unprofessional eagerness to collect his fee, and, seemingly, all to no purpose, unless he had merely desired to keep the detective and Doctor Vanderpool guessing. But surely his motive went deeper than that.
It now appeared obvious that his motive had been one of revenge, but that did not account for the failure to keep the huge sum he had obtained. He was believed to be a comparatively poor man, one to whom a cool quarter of a million would have meant a good deal.
Whatever his reason for committing so ruthless and revolting a crime, why had he not kept his ill-earned fee? It could hardly be that he had any moral scruples about doing so. Nick had sometimes suspected that Grantley was merely the tool of one or more of the millionaire’s financial rivals, but the fact that he had looked elsewhere for his pay need not have prevented him from putting his hand into the pockets of his employers and his victim.
The most likely theory seemed to be that the surgeon had realized, too late, that he was probably being watched and would not be allowed to make away with the proceeds of the check. In that case he might have seen that it was practically valueless to him, and suddenly decided to tear it up and send it to the detective—a spectacular act of defiance that would have been characteristic enough of him.
But even that explanation involved many difficulties.
Grantley was not the man to have failed to look ahead and take account of all the difficulties in advance. That was one objection, and there were others almost equally as strong.
On the whole, therefore, the detective was obliged to admit to himself that this last tangle in the line would be far from easy to unravel.
Fortunately, however, it might be ignored for the present, and later on it was possible that it could be cut out instead of untangled. In other words, whatever the motive, the crime had undoubtedly been committed by Grantley and his assistant, with the connivance of the nurse, at least.
Consequently, the hunt for motives could well wait until after the hunt for the men themselves had been carried to a successful conclusion.