"Nay, I don't think she did," replied Hudson. "Of course, the thing was over in a second. I made no sign that I'd seen aught particular, and she said nought. But—I saw!"

Just then other customers came in, and the bar-keeper turned away to attend to their wants. Hollis and Hetherwick moved from the counter to one of the snug corners at the farther end of the room.

"Whoever she may be, wherever she may be—as Hudson said just now," remarked Hollis, "and if this woman really had anything to do with the mysterious circumstances of Hannaford's death, she ought not to be difficult to find. A woman who carries an indefaceable mark like that on her arm, and whose picture has recently appeared in a newspaper, should easily be traced."

"I think I shall get at her through the picture," agreed Hetherwick. "The newspaper production seems to have been done from a photograph which, from its clearness and finish, was probably taken by some first-class firm in London. I shall go round such firms as soon as I get back. It may be, of course, that she's nothing whatever to do with Hannaford's murder, but still, it's a trail that's got to be followed to the end now that one's started out on it. Well! that seems to finish my business here—as far as she's concerned. But there's another matter—I told you that when Hannaford came to town he had on him a sealed packet containing the secret of some invention or discovery, and that it's strangely and unaccountably missing. His granddaughter says that he worked this thing out—whatever it is—in a laboratory that he had in his garden. Now then, before I go I want to see that laboratory. As he's only recently left the place, I suppose things will still be pretty much as he left them at his old house. Where did he live?"

"He lived on the outskirts of the town," replied Hollis. "An old-fashioned house that he bought some years ago—I know it by sight well enough, though I've never been in it. I don't suppose it's let yet, though I know it's being advertised in the local papers. Let's get some lunch at the 'White Bear,' and then we'll drive up there and see what we can do. You want to get an idea of what it was that Hannaford had invented?"

"Just so," assented Hetherwick. "If the secret was worth all that he told his granddaughter it was, he may have been murdered by somebody who wanted to get sole possession of it. Anyway, it's another trail that's got to be worked on."

"I never heard of Hannaford as an inventor or experimenter," remarked Hollis. "But there, I knew little about him, except in his official capacity: he and his granddaughter, and an elderly woman they kept as a working housekeeper, were quiet sort of folk. I knew that he brought up his granddaughter from infancy, and gave her a rattling good education at the Girls' High School, but beyond that, I know little of their private affairs. I suppose he amused himself in this laboratory you speak of in his spare time?"

"Dabbled in chemistry, I understand," said Hetherwick. "And, if it hasn't been dismantled, we may find something in that laboratory that will give us a clue of some sort."

Hollis seemed to reflect for a minute or two.

"I've an idea!" he said suddenly. "There's a man who lunches at the 'White Bear' every day—a man named Collison; he's analytical chemist to a big firm of dyers in the town. I've seen him in conversation with Hannaford now and then. Perhaps he could tell us something on this point. Come on! this is just about his time for lunch."