was a ruse of terrifying simplicity
but diabolical ingenuity. The wick of the tinder-lighter was an
admirable slow match, obtainable in any tobacconist's shop for a few
pence, which, by means of this trick, had established a false alibi for
the actual murderer by causing the report which had reached the
dining-room, and sent the inmates hastening upstairs to ascertain the
cause. The shot which had mortally wounded Mrs. Heredith must have been
fired before.

How long before? Obviously not very long. That would have been dangerous
to the murderer's plans. He had to consider two things. There was the
chance of somebody entering the room before the false charge exploded,
and the possibility that the coldness of the body of his victim might
arouse medical suspicions. Colwyn did not think that the criminal had
avoided killing Mrs. Heredith so as to ensure against that risk of
discovery. The infliction of a mortal wound which failed to cause
immediate death not only required a high degree of anatomical knowledge,
but left the door open to a dying confession which might have upset the
whole plan. Fate had helped the murderer to that extent.

But the murderer owed more than that to Fate. It was to that grim
goddess he was indebted for the last wonderful touch of actuality which
lifted the whole contrivance so superbly above the realm of artifice.
Suspicion was in the last degree unlikely in any case, but Hazel Rath's
entry and loud scream, just before the moment fixed for the explosion,
ensured complete success by adding a natural verisimilitude which might
have deceived the very Spirit of Truth. Colwyn esteemed himself
fortunate indeed in lighting on what he believed to be the facts. Who
could have imagined a situation in which whimsical Destiny had
ironically stooped down from her high place to dabble ignobly in a
murderer's ghastly plot?

The one point which perplexed Colwyn was the successful concealment of
the pistol on the night of the murder. That part of the plan was as
essential to the murderer as the false report, but it seemed strange
that the pistol had not been discovered when the room was searched. An
examination of the grate upstairs might reveal the reason.

Before leaving the gun-room Colwyn replaced one of the pistols and
restored the case as he had found it to its original position. He
carried away with him the pistol which had been used.

When he reached the upstairs bedroom he locked the door before
pr