She had so few frocks, and these few had to be chosen with so much regard to utility, that there was a uniformity about them which might well pall upon a girl who loved pretty things.

The best frock was a severely plain garment of dark-blue woollen stuff, but it was relieved by a shirt of soft white muslin, and, because a pretty girl always looks charming in a plain frock, Katherine in her dark blue was simply bewitching.
Phil rowed her over the river, bragging all the way of the manner in which he was beginning to handle the oars.

And then, at Katherine's suggestion, he waited to see if Mr.Selincourt would go over and visit the store for an hour or so.
Katherine found Mary lying on a couch under the open window, looking pale and worn, with a very tired expression.

Mr.
Selincourt was reading to her, but when Katherine suggested the waiting boat, and 'Duke Radford's loneliness, she at once declared her father ought to go over and pay the invalid a visit.
"You have been shut up with a fractious convalescent nearly the whole day, dear Daddy, and I am sure it will be a pleasant change to go and chat with Mr.Radford, who is always serene," she said urgently; and so, more to please her than himself, her father said he would go.
"Come down and see me into the boat, Miss Katherine; it won't hurt Mary to be alone, and I want to say thank you for coming to the rescue so promptly the other day," he said.
"I don't want to be thanked, but I will show you the way to the boat with pleasure, if you are afraid of getting lost _en route_," Katherine said with a laugh, but falling into his mood, because she saw he wished to say something to her alone.
When they were beyond earshot of the open window, he said anxiously: "Don't you think Mary looks very badly ?" "She looks fearfully tired," Katherine answered.
"Yes, that is it.

And the tiredness comes from mental strain.
Poor Mary! It seems so hard for her to be happy, yet in all her life she has never lacked anything she wanted save one, and even that I am in hopes she will get yet, if only she has the patience to wait for it." Katherine's heart gave a painful bound.