When they had disappeared Sofia began to think.

There was something more in this affair than mere coincidence, there was mystery, a sinister question.

Her countenance grew as dark as the complexion of her reverie.  Athwart the field of her abstracted vision drifted the figure of young Mr. Karslake.  She was barely conscious of it.

He seated himself with plain premeditation directly opposite the caisse, staring openly.  But Sofia did not heed him at all.  An odd smile shadowed his lips, an expression half eager, half apprehensive; there was a hint of puzzlement in his scrutiny.  It was rather as if he had unexpectedly found some new reason for thinking the girl an exceptionally interesting personality.  But she continued all unaware.

Shortly after being served with a drink which he ordered but made no offer to taste, he moved as if minded to rise and cross to Sofia, sat up and edged forward on the wall-seat with a singular air of timidity and embarrassment.  But whatever his intention, he reconsidered and sat back, glancing round the room to see if anybody were watching him.  He could not see that anybody was.  Not even Sofia.  Relieved, he settled back, found a handsome gold case in the waistcoat of his dinner jacket, extracted a cigarette, nipped it between his lips—­and forgot to light it.

Of a sudden Sofia had arrived at a decision; and with every expression of it in her manner she slipped down from the high stool and left the caisse to take care of itself.  Turning to the swing door she barged through with a high head and fire of determination illuminating her face.  She had had enough of riddles.

Behind the zinc an elderly and trusted waiter was nodding.  The kitchen was cold and dark for the night.  Papa Dupont, then, would be upstairs, closeted with the genius of the establishment.

From the pantry a narrow staircase led up to the apartment above the restaurant.  Sofia mounted rapidly, with a firm tread that was nevertheless practically noiseless, thanks to the paper-thin soles of well-worn slippers.  She could hear voices bickering above.

At the top there was a short, dark corridor, with three doors.  Two of these were closed on sleeping-rooms; the third door, to a sort of combination office and living-room, stood open, letting out a stream of light.

Sofia approached on tiptoe, though the altercation going on within had reached a stage so acute that it was doubtful whether either of the disputants would have heard had she stumped like a navvy.

The point of dissension was not at first apparent, because Mama Therese was speaking, and what she said had exclusively to do with her estimate of Dupont’s character, the mettle of his spirit, the stuff of his mentality, the authenticity of his pedigree (with especial reference to the virtue of his maternal ancestry) and the circumstances of his upbringing; which estimate in sum was low but by no means so low as the terms in which Mama Therese was inspired to couch it.