"Yes."
"On the evening of her death?"
"Yes."
"Bagshot testifies that when she left the room, at nine, Mrs. Heathcote was writing. Was that this letter to you?"
"I presume it was."
"When and how was it mailed? Or rather, what is the date of the postmark?"
"The next morning."
Dexter looked at her searchingly. "This may prove to be very important," he said.
"I know it—now."
"Why have you not spoken before?"