Sue a Little Heroine by L.T. Meade

Connie went downstairs and stood in the doorway. She had gone through a good deal during these last adventurous weeks, and although still it seemed to those who knew her that Connie had quite the prettiest face in all the world, it was slightly haggard now for a girl of fourteen years, and a little of its soft plumpness had left it.

Connie had never looked more absolutely pathetic than she did at this moment, for her heart was full of sorrow for Giles and of anxiety with regard to Sue. She would keep her promise to the little boy -- she would find Sue.