The Octoroon by Mary Elizabeth Braddon

Tristan, the negro, sat in his little chamber, in that quarter of Don Juan's splendid mansion, which was devoted solely to the slaves.

A dark and gloomy shadow rested upon the inky brow of the negro. For some time past the watchful eye of his mother, the old negress, Zarah, had detected her son's unhappiness, but she sought in vain to penetrate the cause. There was much of the savage in the character of this man, and even in his mother he sometimes inspired alarm and suspicion.