Yes, here was the clue to the mystery.

John Saltram had grown tired of his stolen bride--had sighed for his freedom.

Who should say that he had not taken some iniquitous means to rid himself of the tie that had grown troublesome to him?
Gilbert Fenton remembered Ellen Carley's suspicions.

He was no longer inclined to despise them.
It was dreary work to sit by the bedside watching that familiar face, to which fever and delirium had given a strange weird look; dismal work to count the moments, and wonder when that voice, now so thick of utterance as it went on muttering incoherent sentences and meaningless phrases, would be able to reply to those questions which Gilbert Fenton was burning to ask.
Was it a guilty conscience, the dull slow agony of remorse, which had stricken this man down--this strong powerfully-built man, who was a stranger to illness and all physical suffering?
Was the body only crushed by the burden of the mind?
Gilbert could not find any answer to these questions.

He only knew that his sometime friend lay there helpless, unconscious, removed beyond his reach as completely as if he had been lying in his coffin.
"O God, it is hard to bear!" he said half aloud: "it is a bitter trial to bear.