His adversary, with a long snarl of oaths, sprang forward and with a great sweep of his arm slapped the apothecary on the cheek.

And then-- What a silence! Frowenfeld had advanced one step; his opponent stood half turned away, but with his face toward the face he had just struck and his eyes glaring up into the eyes of the apothecary.

The semicircle was dissolved, and each man stood in neutral isolation, motionless and silent.

For one instant objects lost all natural proportion, and to the expectant on-lookers the largest thing in the room was the big, upraised, white fist of Frowenfeld.

But in the next--how was this?
Could it be that that fist had not descended?
The imperturbable Valentine, with one preventing arm laid across the breast of the expected victim and an open hand held restrainingly up for truce, stood between the two men and said: "Professor Frowenfeld--one moment--" Frowenfeld's face was ashen.
"Don't speak, sir!" he exclaimed.