d not start out to
inquire for the slamming door. Why did your guilty couple do all this,
Watson?"

"I confess that I can't explain it."

"Then again, if a woman and her lover conspire to murder a husband,
are they going to advertise their guilt by ostentatiously removing his
wedding ring after his death? Does that strike you as very probable,
Watson?"

"No, it does not."

"And once again, if the thought of leaving a bicycle concealed outside
had occurred to you, would it really have seemed worth doing when the
dullest detective would naturally say this is an obvious blind, as the
bicycle is the first thing which the fugitive needed in order to make
his escape."

"I can conceive of no explanation."

"And yet there should be no combination of events for which the wit of
man cannot conceive an explanation. Simply as a mental exercise, without
any assertion that it is true, let me indicate a possible line of
thought. It is, I admit, mere imagination; but how often is imagination
the mother of truth?

"We will suppose that there was a guilty secret, a really shameful
secret in the life of this man Douglas. This leads to his murder by
someone who is, we will suppose, an avenger, someone from outside.
This avenger, for some reason which I confess I am still at a loss
to explain, took the dead man's wedding ring. The vendetta might
conceivably date back to the man's first marriage, and the ring be taken
for some such reason.

"Before this avenger got away, Barker and the wife had reached the room.
The assassin convinced them that any attempt to arrest him would lead
to the publication of some hideous scandal. They were converted to
this idea, and preferred to let him go. For this purpose they probably
lowered the bridge, which can be done quite noiselessly, and then raised
it again. He made his escape, and for some reason thought that he could
do so more safely on foot than on the bicycle. He therefore left his
machine where it would not be discovered until he had got safely away.
So far we are within the bounds of possibility, are we not?"

"Well, it is possible, no doubt," said I, with some reserve.

"We have to remember, Watson, that whatever occurred is certainly
something very extraordinary. Well, now, to continue our supposititious
case, the couple--not necessarily a guilty couple--realize after the
murderer is gone that they have placed themselves in a position in
which it may be difficult for them to prov