Across the Stream by E.F. Benson

Lady Davidstow and Miss Bampton were sitting together that night in Lady Davidstow's bedroom. She had sent her maid away, saying that she would not want her again that night, and now she held in her hand the sheet of paper covered with lines of meaningless scribbles, with the one intelligible sentence at the end, which Archie had written that day when he should have been doing his copy. In the other hand she held a letter written in ink that was now rather faded, and she was comparing the two. She looked at them for some time in silence, then turned to Miss Bampton.

"Yes, you are quite right, Cathie," she said. "What Archie wrote might actually be in Martin's handwriting. Look for yourself: there's the last letter he ever wrote to me."