What features of chauvelin make the reader distrust him even though marguerite calls him a friend

The quotes below can all be found in Chapter Eight of the novel. These quotes describe the Chauvelin's features perfectly.

"Chauvelin was then nearer forty than thirty–a clever, shrewd-looking personality, with a curious fox-like expression in the deep, sunken eyes."

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"She did not notice the sarcastic little smile, however, that hovered round the thin lips of Chauvelin."

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"Chauvelin stood beside her, his shrewd, pale, yellow eyes fixed on the pretty

face, which looked so sweet and childlike in this soft English summer twilight."

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Chauvelin took another pinch of snuff: he seemed very much addicted to that pernicious habit, so prevalent in those days; perhaps, too, he found the taking of snuff a convenient veil for disguising the quick, shrewd glances with which he

strove to read the very souls of those with whom he came in contact."