andled the powder
better. You have done this before, Cupples, I can see. You are an old
hand.'

'I really am not,' said Mr Cupples seriously, as Trent returned the
fallen powder to the bottle. 'I assure you it is all a complete mystery
to me. What did I do then?'

'I brush the powdered part of the bowl lightly with this camel-hair
brush. Now look at it again. You saw nothing odd about it before. Do you
see anything now?'

Mr Cupples peered again. 'How curious!' he said. 'Yes, there are two
large grey finger-marks on the bowl. They were not there before.'

'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 coul