Let us pass over that scene.

She also wrote to Eugene, addressing the letter to Millstead Manor.

Eugene was not at Millstead Manor; and if Ayre had hastily assumed that his _fiancee_ would be in possession of his address, was it her business to undeceive him?
She was by no means inclined to do one jot more than fulfill the letter of her bond--whereby it came to pass that Eugene did not receive the letter for nearly two months and did not know of his recovered liberty all that time.

For Haddington, in his joy, easily promised silence for a little while; it seemed only decent; and even Ayre could not refuse to agree with him that, though Eugene must be told, nobody else ought to be until Eugene had formally signified his assent to the lady's transfer.

Ayre could not take upon himself, on his friend's behalf, the responsibility of dispensing with this ceremony, though he was sure it would be a mere ceremony.
As for Ayre himself, when his task was done he straightway fled from Baden.