Bardelys the Magnificent by Rafael Sabatini

In the days that followed I saw much of the Chevalier de Saint-Eustache. He was a very constant visitor at Lavedan, and the reason of it was not far to seek. For my own part, I disliked him - I had done so from the moment when first I had set eyes on him - and since hatred, like affection, is often a matter of reciprocity, the Chevalier was not slow to return my dislike. Our manner gradually, by almost imperceptible stages, grew more distant, until by the end of a week it had become so hostile that Lavedan found occasion to comment upon it.

-"Beware of Saint-Eustache," he warned me. "You are becoming very manifestly distasteful to each other, and I would urge you to have a care. I don't trust him. His attachment to our Cause is of a lukewarm character, and he gives me uneasiness, for he may do much harm if he is so inclined. It is on this account that I tolerate his presence at Lavedan. Frankly, I fear him, and I would counsel you to do no less. The man is a liar, even if but a boastful liar and liars are never long out of mischief."