“Well,” returned Nares, with the same unamiable reserve, “for a reason, which I guess you know, the cruise may suit me; but there's a point or two to settle. We shall have to talk, Mr. Pinkerton. But whether I go or not, somebody will; there's no sense in losing time; and you might give Mr. Johnson a note, let him take the hands right down, and set to to overhaul the rigging. The beasts look sober,” he added, with an air of great disgust, “and need putting to work to keep them so.”
This being agreed upon, Nares watched his subordinate depart and drew a visible breath. “And now we're alone and can talk,” said he. “What's this thing about? It's been advertised like Barnum's museum; that poster of yours has set the Front talking; that's an objection in itself, for I'm laying a little dark just now; and anyway, before I take the ship, I require to know what I'm going after.”
Thereupon Pinkerton gave him the whole tale, beginning with a businesslike precision, and working himself up, as he went on, to the boiling-point of narrative enthusiasm. Nares sat and smoked, hat still on head, and acknowledged each fresh feature of the story with a frowning nod. But his pale blue eyes betrayed him, and lighted visibly.
What do you take I'm laying a little dark to mean in this context? I think it's slang and it has to be I'm lying a little dark.