There came a time when Mrs. Bunting, looking back—­as even the least imaginative of us are apt to look back to any part of our own past lives which becomes for any reason poignantly memorable —­wondered how soon it was that she had discovered that her lodger was given to creeping out of the house at a time when almost all living things prefer to sleep.

She brought herself to believe—­but I am inclined to doubt whether she was right in so believing—­that the first time she became aware of this strange nocturnal habit of Mr. Sleuth’s happened to be during the night which preceded the day on which she had observed a very curious circumstance.  This very curious circumstance was the complete disappearance of one of Mr. Sleuth’s three suits of clothes.

It always passes my comprehension how people can remember, over any length of time, not every moment of certain happenings, for that is natural enough, but the day, the hour, the minute when these happenings took place!  Much as she thought about it afterwards, even Mrs. Bunting never quite made up her mind whether it was during the fifth or the sixth night of Mr. Sleuth’s stay under her roof that she became aware that he had gone out at two in the morning and had only come in at five.

But that there did come such a night is certain—­as certain as is the fact that her discovery coincided with various occurrences which were destined to remain retrospectively memorable.

******

It was intensely dark, intensely quiet—­the darkest quietest hour of the night, when suddenly Mrs. Bunting was awakened from a deep, dreamless sleep by sounds at once unexpected and familiar.  She knew at once what those sounds were.  They were those made by Mr. Sleuth, first coming down the stairs, and walking on tiptoe—­she was sure it was on tiptoe—­past her door, and finally softly shutting the front door behind him.

Try as she would, Mrs. Bunting found it quite impossible to go to sleep again.  There she lay wide awake, afraid to move lest Bunting should waken up too, till she heard Mr. Sleuth, three hours later, creep back into the house and so up to bed.

Then, and not till then, she slept again.  But in the morning she felt very tired, so tired indeed, that she had been very glad when Bunting good-naturedly suggested that he should go out and do their little bit of marketing.

The worthy couple had very soon discovered that in the matter of catering it was not altogether an easy matter to satisfy Mr. Sleuth, and that though he always tried to appear pleased.  This perfect lodger had one serious fault from the point of view of those who keep lodgings.  Strange to say, he was a vegetarian.  He would not eat meat in any form.  He sometimes, however, condescended to a chicken, and when he did so condescend he generously intimated that Mr. and Mrs. Bunting were welcome to a share in it.

Now to-day—­this day of which the happenings were to linger in Mrs. Bunting’s mind so very long, and to remain so very vivid, it had been arranged that Mr. Sleuth was to have some fish for his lunch, while what he left was to be “done up” to serve for his simple supper.