Mary was a leaker

[RJNorton]

As recently as 2008 this apocryphal story continues to be seen in books. This is from Daniel Epstein's The Lincolns: Portrait of a Marriage.

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The guard at the door admitted the president, but was too tongue-tied to announce him. This was unprecedented. A senator later told the postmaster-general: "There at the foot of the table, standing solitary, his hat in his hand, his form towering above the committee members, Abraham Lincoln stood. Had he come by some incantation, thus of a sudden appearing before us unannounced, we could not have been more astounded. The pathos written upon his face, the almost inhuman sadness in his eyes...and above all an indescribable sense of his complete isolation - the sad solitude which is inherent in all true grandeur of character and intellect - all this revealed Lincoln to me."

No one had any idea what to say, so they sat still and silent. The committee had not summoned him, and they did not know he was aware they were about to "investigate the reports, which, if true, fastened treason upon his family in the White House." When the President at last broke the silence, he spoke in the most sorrowful tone: “I, Abraham Lincoln, President of the United States, appear of my own volition before this committee of the Senate to say that I, of my own knowledge, know that it is untrue that any of my family hold treasonable communication with the enemy.”

Again a heavy silence descended upon the room as Lincoln looked into the eyes of the men around the table. Then he turned and was gone "as silently and solitary as he came." So without any formal discussion, the committees in the Senate and the House, Ben Wade and John Hickman, "dropped all consideration of the rumors that the wife of the President was betraying the Union...We were so greatly affected that the committee adjourned for the day."