"In a seemingly purposeless murder like this, a certain amount of suspicion gathers round the other members of the household. Human nature being what it is, one should never take anything for granted, but should always be on the watch for hidden motives. But in this case the members of the household, with the exception of Miss Heredith, were downstairs in the dining-room at the time the murder was committed. Miss Heredith left the room a few minutes before the shot was heard. You will recall that she volunteered that statement to us this morning. It occurred to me at the time that that may have been bluff to put us off the scent. Clever criminals often do that kind of thing. My suspicions against her were strengthened by the additional fact that Miss Heredith did not like her nephew's wife. She masked the fact beneath a well-bred semblance of grief and horror, but it was plain as a pikestaff to me. But, after thinking over all the circumstances, I came to the conclusion that she had nothing whatever to do with it." "Such a possibility is inconceivable," exclaimed Captain Stanhill. "A lady like Miss Heredith would never commit murder." "It was not for that reason that I excluded her from suspicion," replied Merrington drily. "The points against her were really very damaging. She was out of the dining-room when the scream was heard, and when the others rushed out of the dining-room on hearing the shot, the first thing they saw was Miss Heredith descending the staircase of the wing in which her nephew's wife had been murdered. Fortunately for Miss Heredith, she was almost at the bottom of the staircase when she was seen. The guests streamed out of the dining-room directly the shot was heard, therefore it is impossible that Miss Heredith could have shot Violet Heredith and then reached the bottom of the stairs so quickly. She is able to establish an alibi of time, by, perhaps, half a minute. "As all the members of the house party were in the dining-room at the time, it is clear that they had nothing to do with the actual commission of the crime. The next thing is the servants, and they also can be excluded from suspicion. When we examined them this morning they were all able to prove, more or less conclusively, that they were engaged in their various duties at the time the murder was committed. The point is that not one of them was upstairs in the left wing of the house when Mrs. Heredith was shot. "My original impression that the murder was not committed by a native of the district has been deepened by our afternoon's investigations. Where, then, are we to look for the murderer? To answer that question, in part, let us first consider _how_ the murder was committed, and try and reconstruct the circumstances in which the murderer must have entered and left the house.