"Ah!" exclaimed Hetherwick. "I see!"
"We know," continued Mapperley, "that Granett went that evening to see the chemist who gave information about him; we know, too, that he and the chemist went and had a drink together, and parted at about closing time, Granett then, according to the chemist, going towards Victoria Street. Now I think that Granett then met Hannaford—accidentally. They'd known each other in Sellithwaite. They talked—Granett told Hannaford he was down on his luck. Hannaford, evidently, was a kind-hearted man, and I think he did two things out of kindness for Granett. He gave him that five-pound note——"
"That was got at Vivian's!" interrupted Hetherwick quickly.
"To be sure!" assented Mapperley. "But we know that Hannaford had been at Vivian's—with Baseverie—undoubtedly. Taken there by Baseverie, which makes me certain that for two or three days before his death he'd been in touch with both Baseverie and Ambrose. Hannaford got that fiver in change at Vivian's. And he gave it to Granett, on hearing his story. But he did something else—something that was far more important—that is far more important—to us!"
"What?" asked Hetherwick.
"He turned back to the place he'd just left, and took Granett with him!" answered Mapperley with confidence. "He knew Granett was a trained and qualified chemist; he thought he could get him a job with these men who, presumably, were going to take up his own invention. It would be little more than half-past ten then. Where else than at this place are Hannaford and Granett likely to have been between that time and the time at which they got into your carriage at St. James's Park? Of course they were there—with Ambrose and Baseverie."
"As you put it—highly probable," said Hetherwick. "Two and a half hours—doing what?"
"Ah, now we come to the real thing!" exclaimed Mapperley. "My own belief is that Hannaford was fatally poisoned when he left those two men the first time! They'd two objects in poisoning him—or, to put it another way, he'd entrusted them with two secrets—one about Madame Listorelle; the other about his invention. They wanted to keep both to themselves and to profit by both. The invention, no doubt, has considerable value—Hannaford believed it had, anyway. They thought they could blackmail Madame and her sister, Lady Riversreade. So, before Hannaford left them the first time, they poisoned him—cleverly, subtly, devilishly—knowing that so many hours would elapse before the poison worked, and that by that time he'd be safe in bed at his hotel and would die in his sleep. But—he went back to them again, and took another man with him! So—that man had to die, too!"
Hetherwick thought awhile in silence.
"All very good theory, Mapperley," he said at last. "But—it may be nothing but theory. Why did Granett run off at Charing Cross?"