Trevelyan had not heard the words.

He had walked on, making the distance between him and the other man greater than was necessary, anxious to show to his wife that he had no jealousy at such a meeting as this.
But his wife was determined that she would put an end to this state of things, let the cost be what it might.

She did not say a word to Colonel Osborne, but addressed herself at once to her husband.
"Louis," she said, "will you give me your arm?
We will go back, if you please." Then she took her husband's arm, and turned herself and him abruptly away from their companion.
The thing was done in such a manner that it was impossible that Colonel Osborne should not perceive that he had been left in anger.
When Trevelyan and his wife had gone back a few yards, he was obliged to return for Nora.

He did so, and then rejoined his wife.
"It was quite unnecessary, Emily," he said, "that you should behave like that." "Your suspicions," she said, "have made it almost impossible for me to behave with propriety." "You have told him everything now," said Trevelyan.
"And it was requisite that he should be told," said his wife.

Then they walked home without interchanging another word.