"Why should I doubt it? Some one must have existed who was sufficiently familiar with the house to go about in it in the middle of the day without attracting any one's attention."
"In the middle of the day?" he said with a chuckle.
"Any time after 8.30 in the morning."
"So you, too, believe in the 'caretaker, wrapped up in a shawl,' cleaning her front steps?" he queried.
"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—"