“But—­”

“It never struck you, in spite of the training your intercourse with me must have given you, that the person who carefully did all the work in the Rubens Studios, laid the fires and carried up the coals, merely did it in order to gain time; in order that the bitter frost might really and effectually do its work, and Mrs. Owen be not missed until she was truly dead.”

“But—­” suggested Polly again.

“It never struck you that one of the greatest secrets of successful crime is to lead the police astray with regard to the time when the crime was committed.  That was, if you remember, the great point in the Regent’s Park murder.

“In this case the ‘nephew,’ since we admit his existence, would—­even if he were ever found, which is doubtful—­be able to prove as good an alibi as young Greenhill.”

“But I don’t understand—­”

“How the murder was committed?” he said eagerly.  “Surely you can see it all for yourself, since you admit the ’nephew’—­a scamp, perhaps—­who sponges on the good-natured woman.  He terrorises and threatens her, so much so that she fancies her money is no longer safe even in the Birkbeck Bank.  Women of that class are apt at times to mistrust the Bank of England.  Anyway, she withdraws her money.  Who knows what she meant to do with it in the immediate future?

“In any case, she wishes to secure it after her death to a young man whom she likes, and who has known how to win her good graces.  That afternoon the nephew begs, entreats for more money; they have a row; the poor woman is in tears, and is only temporarily consoled by a pleasant visit at the theatre.

“At 2 o’clock in the morning young Greenhill parts from her.  Two minutes later the nephew knocks at the door.  He comes with a plausible tale of having missed his last train, and asks for a ‘shake down’ somewhere in the house.  The good-natured woman suggests a sofa in one of the studios, and then quietly prepares to go to bed.  The rest is very simple and elementary.  The nephew sneaks into his aunt’s room, finds her standing in her nightgown; he demands money with threats of violence; terrified, she staggers, knocks her head against the gas bracket, and falls on the floor stunned, while the nephew seeks for her keys and takes possession of the L800.  You will admit that the subsequent mise en scene—­is worthy of a genius.

“No struggle, not the usual hideous accessories round a crime.  Only the open windows, the bitter north-easterly gale, and the heavily falling snow—­two silent accomplices, as silent as the dead.

“After that the murderer, with perfect presence of mind, busies himself in the house, doing the work which will ensure that Mrs. Owen shall not be missed, at any rate, for some time.  He dusts and tidies; some few hours later he even slips on his aunt’s skirt and bodice, wraps his head in a shawl, and boldly allows those neighbours who are astir to see what they believe to be Mrs. Owen.  Then he goes back to her room, resumes his normal appearance and quietly leaves the house.”