The quote captures a foreboding scene where the horizon is obscured by dark clouds, suggesting an impending storm or danger. The placid waterway, usually a symbol of peace and exploration, appears somber and leads to an uncertain fate, representing a journey into the unknown. This imagery evokes feelings of unease and anticipation, highlighting the contrast between calmness and the looming darkness.

In Joseph Conrad's "Heart of Darkness," this passage serves as a metaphor for the protagonist's impending voyage into both literal and metaphorical darkness. As the characters prepare to navigate this murky expanse, it symbolizes their confrontation with the unknown, both in terms of exploration and the complexities of human nature. The overcast sky, rich with ominous implications, foreshadows the challenges and moral ambiguities they will encounter on their journey.