Do you know Monsieur de Treville, their captain ?" "Oh, yes, him! I know him; not personally, but from having heard the queen speak of him more than once as a brave and loyal gentleman." "You do not fear lest he should betray you to the cardinal ?" "Oh, no, certainly not!" "Well, reveal your secret to him, and ask him whether, however important, however valuable, however terrible it may be, you may not confide it to me." "But this secret is not mine, and I cannot reveal it in this manner." "You were about to confide it to Monsieur Bonacieux," said d'Artagnan, with chagrin.
"As one confides a letter to the hollow of a tree, to the wing of a pigeon, to the collar of a dog." "And yet, me--you see plainly that I love you." "You say so." "I am an honorable man." "You say so." "I am a gallant fellow." "I believe it." "I am brave." "Oh, I am sure of that!" "Then, put me to the proof." Mme.Bonacieux looked at the young man, restrained for a minute by a last hesitation; but there was such an ardor in his eyes, such persuasion in his voice, that she felt herself constrained to confide in him.

Besides, she found herself in circumstances where everything must be risked for the sake of everything.

The queen might be as much injured by too much reticence as by too much confidence; and--let us admit it--the involuntary sentiment which she felt for her young protector decided her to speak.
"Listen," said she; "I yield to your protestations, I yield to your assurances.

But I swear to you, before God who hears us, that if you betray me, and my enemies pardon me, I will kill myself, while accusing you of my death." "And I--I swear to you before God, madame," said d'Artagnan, "that if I am taken while accomplishing the orders you give me, I will die sooner than do anything that may compromise anyone." Then the young woman confided in him the terrible secret of which chance had already communicated to him a part in front of the Samaritaine.

This was their mutual declaration of love.
D'Artagnan was radiant with joy and pride.