It was addressed to the late Earl, and was open.

She hesitated a moment, then, with a strange premonition and a tightening of her heart-strings, she spread it out and read it.
At first she could scarcely see because of the mist in her eyes; but presently her sight cleared, and she read quickly, her cheeks burning with excitement, her heart throbbing violently.

The letter was the last expression of a disappointed and barren life.

The slow, stammering tongue of an almost silent existence had found the fulness of speech.
The fountains of the deep had been broken up, and Sybil Eglington's repressed emotions, undeveloped passions, tortured by mortal sufferings, and refined and vitalised by the atmosphere blown in upon her last hours from the Hereafter, were set free, given voice and power at last.
The letter reviewed the life she had lived with her husband during twenty-odd years, reproved herself for not speaking out and telling him his faults at the beginning, and for drawing in upon herself, when she might have compelled him to a truer understanding; and, when all that was said, called him to such an account as only the dying might make--the irrevocable, disillusionising truth which may not be altered, the poignant record of failure and its causes.
"...

I could not talk well, I never could, as a girl," the letter ran; "and you could talk like one inspired, and so speciously, so overwhelmingly, that I felt I could say nothing in disagreement, not anything but assent; while all the time I felt how hollow was so much you said--a cloak of words to cover up the real thought behind.