“You want to get to work at once, Patsy, while the trail is warm.”

Patsy hurried away, and Ida, saying that, unless the chief had further instructions, she would go, too, followed the lad out of the apartment.

“Now, Chick,” said Nick. “To send Edith to Mrs. Constant, and then you and I will take up the most difficult part of the work.”

In a few moments these two shrewd detectives were on their way to the neighborhood of the Constant residence. As they were riding uptown in the car, Nick said:

“Mrs. Constant’s theory is that Ethel was killed by a person who had intended to kill her, but was misled by the strong resemblance between Ethel and herself.

“That resemblance is great,” admitted Nick. “I was misled by it myself twice—once shortly after I had been introduced to Mrs. Constant, and again when Ethel brought that package to me from Blanche Constant.”

“But, chief,” said Chick, “you did not know at that time that Mrs. Constant had a twin sister; the mistake was a natural one. But if Masson was as well acquainted with Mrs. Constant as he seems to be it would be strange if he did not know of that twin sister.”

“And would not have been easily misled,” said Nick. “You have struck a point that must be investigated.”

“And there is a point on the other side,” said Chick. “The hard thing in adopting the theory of Mrs. Constant is that a man of the kind Masson is should commit murder, especially in cold blood.

“Now, suppose that Masson did not know of the twin sister, suppose he climbed into that coach under the notion that Mrs. Constant was in it. Since it was Ethel Romney, she, of course, denied that she was Blanche or that she knew Masson, perhaps, to his anger, leading to the murder and the reason for it.”