Tea at Carslake's that day was the usual cheery meal, and if Kitty and Duane were unusually quiet and silent no one gave much heed to them. Consequently, it was quite a shock to all except Kitty and Duane when, directly tea was over, the house mistress gave the order to assemble at once in the hall. "What on earth's up now?" exclaimed Hilary, as the little party of seniors made their way across the quad to the school building on the heels of their juniors. "Duane, do you know?" The head prefect paused a moment before she answered, "Yes, I think so, but you'll know all about it in a few minutes." As she spoke they entered the hall, finding it nearly full, with rank after rank of waiting girls, all talking in subdued murmurs that now and again broke into a clamorous buzz. Silence fell abruptly as Miss St. Leger entered and took her place on the dais at the farther end of the hall. The girls stood in their house places, Sheerston's and Carslake's on the right of the wide central gangway, Prince's and Green's on the left. The Principal then gave the signal for calling-over, a customary formality which only took place on special occasions, and the four head prefects began rapidly calling the names of the girls in their own houses, each girl answering, "Present." With the calling-over the interest in the proceedings increased, if possible, everyone being given the impression that the occasion was a serious one. Amidst a breathless hush, the Principal began to speak. "You will be wondering, I know, why I have assembled the whole school so suddenly. I am sorry to say that the reason is a very unpleasant one. It is this. A deliberate attempt was made to spoil the chances of one of the Richoter candidates in the practical examination which, as you all know, took place to-day. You will be still more surprised to hear," pausing as an amazed gasp ran round the room, "that the girl upon whom this despicable trick was attempted is one of the most well-liked and esteemed--perhaps the most popular girl in the school, the head prefect of Sheerston's." A low murmur was heard and all heads turned involuntarily towards Salome, who coloured all over her frank, open face, then paled as swiftly. "That this silly, stupid attempt failed most lamentably does not, to me, make it any the less serious." The Principal then proceeded to explain the nature of the experiment the candidates were working, and the apparatus being used. She gave the gist of the inquiry she had held in the laboratory that afternoon, and then went on to say: "So you see, it certainly seems that the only two girls who can throw any light on this affair are Duane and Kitty. If those two girls will come forward I should like to question them again before the school. They have had a little time since my first inquiry to think things over and may have thought of something which did not then occur to them."