The voices appeared to come from a group of passengers enveloped in cloaks and wraps.

It was impossible to recognize them in the dark, though it sometimes happened that, when the steamer's chimney sent forth a plume of ruddy flames, the sparks seemed to fall amongst the group as though thousands of spangles had been suddenly illuminated.
Michael was about to step up the ladder, when a few words reached his ear, uttered in that strange tongue which he had heard during the night at the fair.

Instinctively he stopped to listen.

Protected by the shadow of the forecastle, he could not be perceived himself.

As to seeing the passengers who were talking, that was impossible.