“I am Hawkshaw the detective,” observed Trent. “Would it interest you to hear a short lecture on the subject of glass finger-bowls? When you take one up with your hand you leave traces upon it, usually practically invisible, which may remain for days or months. You leave the marks of your fingers. The human hand, even when quite clean, is never quite dry, and sometimes—in moments of great anxiety, for instance, Cupples—it is very moist. It leaves a mark on any cold smooth surface it may touch. That bowl was moved by somebody with a rather moist hand quite lately.” He sprinkled the powder again. “Here on the other side, you see, is the thumb-mark—very good impressions all of them.” He spoke without raising his voice, but Mr. Cupples could perceive that he was ablaze with excitement as he stared at the faint grey marks. “This one should be the index finger. I need not tell a man of your knowledge of the world that the pattern of it is a single-spiral whorl, with deltas symmetrically disposed. This, the print of the second finger, is a simple loop, with a staple core and fifteen counts. I know there are fifteen, because I have just the same two prints on this negative, which I have examined in detail. Look!”—he held one of the negatives up to the light of the declining sun and demonstrated with a pencil point. “You can see they’re the same. You see the bifurcation of that ridge. There it is in the other. You see that little scar near the centre. There it is in the other. There are a score of ridge-characteristics on which an expert would swear in the witness-box that the marks on that bowl and the marks I have photographed on this negative were made by the same hand.” “And where did you photograph them? What does it all mean?” asked Mr Cupples, wide-eyed. “I found them on the inside of the left-hand leaf of the front window in Mrs. Manderson’s bedroom. As I could not bring the window with me, I photographed them, sticking a bit of black paper on the other side of the glass for the purpose. The bowl comes from Manderson’s room. It is the bowl in which his false teeth were placed at night. I could bring that away, so I did.” “But those cannot be Mabel’s finger-marks.” “I should think not!” said Trent with decision. “They are twice the size of any print Mrs. Manderson could make.” “Then they must be her husband’s.”