Mason laughed. “Believe it or not,” he said, “after having all of the factors for a solution in my hands, I couldn’t put them together.”
“What do you mean, all the factors of the solution?”
“Don’t you remember?” Mason said. “We talked it over and decided that the two people who were involved must be persons who couldn’t afford to be seen together, and who couldn’t communicate by telephone, but who both had access to that basement. We thought about a person being deaf or being so crippled he couldn’t get to a telephone, but the true solution never occurred to me.”
“Which was?” she asked.
“Exceedingly simple. Rebecca could get to the telephone all right when she was called, but only after the children had answered the phone first, and she couldn’t put through outside calls without arousing suspicions because she had lived so much as a recluse.”
“But why couldn’t Wenston simply have called and asked for — oh, I see, — that lisp of his. Anyone would have noticed it at once, and then after the case developed, it would have been commented on. His lisp is sufficiently pronounced so no one would ever forget it, once they had heard it.”
Mason said, “That is it. And, having laid down all of the basic factors for a solution I simply failed to apply them.”
“But I thought you said the voice of the woman who called you was very cultured and...”
“Don’t forget,” Mason said, “Rebecca has remarkable powers of mimicry. Remember the way she imitated Opal Sunley’s voice? She even tried to mimic Mrs. Gentrie’s voice, but she was smart enough to know that she would have to make it sound as though she were in great agony, to cover up any little defects in impersonation. Read me her confession, Della. I want to check certain details.”
Della Street said, “I’ll have to read it from my shorthand notes.”