But then there arose in his mind a doubt that had perplexed him sorely for a long time.

If his successful rival had been indeed a stranger to him, what reason could there be for so much mystery in the circumstances of the marriage?
and why should Marian have so carefully avoided telling him anything about her husband?
That his friend, having betrayed him, should shrink from the revelation of his falsehood, should adopt any underhand course to avoid discovery, seemed natural enough.

Yet to believe this was to think meanly of the man whom he had loved so well, whom he had confided in so implicitly until the arising of this cruel doubt.
He had known long ago, when the first freshness of his boyish delusions faded away before the penetrating clear daylight of reality, he had known long ago that his friend was not faultless; that except in that one faithful alliance with himself, John Saltram had been fickle, wayward, vacillating, unstable, and inconstant, true to no dream of his youth, no ambition of his early manhood content to drop one purpose after another, until his life was left without any exalted aim.

But Gilbert had fancied his friend's nature was still a noble one in spite of the comparative failure of his life.

It was very difficult for him to imagine it possible that this friend could act falsely and ungenerously, could steal his betrothed from him, and keep the secret of his guilt, pretending to sympathise with the jilted lover all the while.
But though Mr.Fenton told himself at one moment that this was impossible, his thoughts travelled back to the same point immediately afterwards, and the image of John Saltram arose before him as that of his hidden foe.