She was going to help to hide something, to live with a strange secret trouble and while she did so must wear her accustomed, respectable and decorous manner and aspect.
Whatsoever alarmed or startled her, she must not seem to be startled or alarmed.

As his lordship had carried himself with his usual bearing, spoken in his high-bred calm voice and not once failed in the naturalness of his expression--even when he had told her the whole strange plan--so she must in any circumstances which arose and in any difficult situation wear always the aspect of a well-bred and trained servant who knew nothing which did not concern her and did nothing which ordinary domestic service did not require that she should do.

She must always seem to be only Sarah Ann Dowson and never forget.

But delicate and unusual as this problem was, it was not the thing which made her heart heavy.

Several times during her journey she had been obliged to turn her face towards the window of the railway carriage and away from her fellow passengers so that she might very quickly and furtively touch her eyes with her handkerchief because she did not want any one to see the tear which obstinately welled up in spite of her efforts to keep it back.
She had heard of "trouble" in good families, had even been related to it.