When does Percy Blakeney reveal his love for Lady Blakeney?

The following dialogue comes from Chapter 17, The Farewell. This is the scene in which Marguerite realizes Percy's love for her.

"How lovely she looked in this morning sunlight, with her ardent hair streaming around her shoulders. He bowed very low and kissed her hand; she felt the burning kiss and her heart thrilled with joy and hope.

"You will come back?" she said tenderly.

"Very soon!" he replied, looking longingly into her blue eyes.

"Any. . .you will remember?. . ." she asked as her eyes, in response to his look, gave him an infinity of promise.

"I will always remember, Madame, that you have honoured me by commanding my services."

The words were cold and formal, but they did not chill her this time. Her woman's heart had read his, beneath the impassive mask his pride still forced him to wear."