What does "black Care" mean in _Uncle Silas_?

What does "black Care" mean in the following passage from Uncle Silas by J.T. Sheridan Le Fanu?

Waiting for the train, as we stood upon the platform, I looked back again toward the wooded uplands of Bartram; and far behind, the fine range of mountains, azure and soft in the distance, beyond which lay beloved old Knowl, and my lost father and mother, and the scenes of my childhood, never embittered except by the sibyl who sat beside me.

Under happier circumstances I should have been, at my then early age, quite wild with pleasurable excitement on entering London for the first time. But black Care sat by me, with her pale hand in mine: a voice of fear and warning, whose words I could not catch, was always in my ear. We drove through London, amid the glare of lamps, toward the West End, and for a little while the sense of novelty and curiosity overcame my despondency, and I peeped eagerly from the window.

Solution 1:

It means worry or apprehension, in this case caused or inspired by the narrator's traveling companion (the governess Madame de la Rougierre, who later turns out to be a sinister character).

In the first paragraph, the narrator refers to the sibyl sitting next to her; it is this self-same sibyl which she later names "black Care". Both terms are cases of anthropomorphism, of the personification of some inhuman or abstract concept. Note the capitalization in "black Care", as if it were a proper noun -- or name.

Knowing that "black Care" is an embodiment of some abstract concept, we need to unpack it to discover which. The entire passage offers numerous clues, but "sibyl" and the adjective "black" modifying "Care" with the qualities of darkness and gloominess are sufficient to resolve the question.

So we only need to open the dictionary and look for senses of "care" which carry the qualifies of darkness, gloominess, and portention or foreboding (indicated by the figurative sibyl, a prophetess).

Thus care, sense 2, from Merriam-Webster:

Care:

2a : a disquieted state of mixed uncertainty, apprehension, and responsibility

2b : a cause for such anxiety

Here, the governess embodies, and is the cause of, the narrator's vaguely directed but intense apprehension.

It's worth noting that the author probably chose the word sybil, a figurative reference to a female prophet, because the governess is literally a woman; it is possible there's a similar interplay of literal and figurative language with black, in that the governess may be literally dressed in black clothing (in mourning for the narrator's late parents), but still figuratively be a dark and foreboding character.

Solution 2:

Dan's answer is entirely correct, but I think it's worth adding that Le Fanu was alluding to a famous Latin quotation Post equitem sedet atra cura, usually translated "Behind the horseman sits black Care", though worry or foreboding would do as well.

When this was written, a good knowledge of Latin and Greek were indispensable for an educated person (in the sense that you could not get into university without them), so all his readers would immediately have appreciated this and other classical references. I understand that these days it is even possible in some places for a non-classicist to obtain an English degree: sic transit gloria mundi.