It was properly secured.

She left the bed-chamber, locking the main door behind her.
Immediately on her departure, the Countess, oppressed by the confined air in the wardrobe, ventured on stepping out of her hiding place into the empty room.
Entering the dressing-room, she listened at the door, until the silence outside informed her that the corridor was empty.

Upon this, she unlocked the door, and, passing out, closed it again softly; leaving it to all appearance (when viewed on the inner side) as carefully secured as Agnes had seen it when she tried the key in the lock with her own hand.
While the Montbarrys were still at dinner, Henry Westwick joined them, arriving from Milan.
When he entered the room, and again when he advanced to shake hands with her, Agnes was conscious of a latent feeling which secretly reciprocated Henry's unconcealed pleasure on meeting her again.

For a moment only, she returned his look; and in that moment her own observation told her that she had silently encouraged him to hope.

She saw it in the sudden glow of happiness which overspread his face; and she confusedly took refuge in the usual conventional inquiries relating to the relatives whom he had left at Milan.
Taking his place at the table, Henry gave a most amusing account of the position of his brother Francis between the mercenary opera-dancer on one side, and the unscrupulous manager of the French theatre on the other.