Miss Ickthorpe said tartly: “You say ‘her.’ But it’s a man’s watch, John—you forget that.” Burrows grinned. “A woman can own a man’s watch, can’t she? Now whose watch was it? Easy. In the back of the case there was a circular patch of fuzzy paper, as if something had been ripped out. What made of paper is usually pasted in the back of a watch? A photograph. Why was it taken out? Obviously, because the murderer’s face was in that photograph. . . . In the last two hours I followed this lead. I visited my suspect on a reportorial pretext and managed to get a look at a photograph-album she has. There I found one photograph with a circular patch cut out. From the rest of the photo it was clear that the missing circle contained the heads of a man and a woman. My case was complete!”

“Perfectly amazing,” murmured Ellery. “And this murderess of yours is—?”

“Spargo’s wife! . . . Motive—hate, or revenge, or thwarted love, or something.”

Miss Ickthorpe sniffed, and Crane shook his head. “Well,” said Ellery, “we seem to be in disagreement. Nevertheless a very interesting analysis, John. . . . Walter, what’s yours?”

Crane hunched his broad shoulders. “I agree with Johnny that the watch did not belong to Spargo, that the murderer set the hands at 10:20 to provide an alibi; but I disagree as to the identity of the criminal. I also worked on the watch as the main clue. But with a vastly different approach.

“Look here.” He brought out the gaudy timepiece and tapped its cracked crystal deliberately. “Here’s something you people may not know. Watches, so to speak, breathe. That is, contact with warm flesh causes the air inside to expand and force its way out through the minute cracks and holes of the case and crystal. When the watch is laid aside, the air cools and contracts, and dust-bearing air is sucked into the interior.”

“I always said I should have studied science,” said Ellery. “That’s a new trick, Walter. Continue.”

“To put it specifically, a baker’s watch will be found to contain flour-dust. A bricklayer’s watch will collect brick-dust.” Crane’s voice rose triumphantly. “D’you know what I found in this watch? Tiny particles of a woman’s face-powder!”

Miss Ickthorpe frowned. Crane continued in a deep voice: “And a very special kind of face-powder it is, Mr. Queen. Kind used only by women of certain complexions. What complexions? Negro brown! The powder came from a mulatto woman’s purse! I’ve questioned her, checked her vanity-case, and although she denies it, I say that Spargo’s murderess is Agatha Robins, the mulatto maid who ‘found’ the body!”

Ellery whistled gently. “Good work, Walter, splendid work. And of course from your standpoint she would deny being the owner of the watch anyway. That clears something up for me. . . . But motive?”