“La Belle Dame sans Merci” is framed as a dialogue between an anonymous speaker and a knight. The poem begins with an apostrophe or address, where the speaker questions a knight in the wilderness. “O” (Line 1) is usually an address used in an ode, sometimes celebratory in tone. Here, the plaintive sound of the “O” is full of lament, foreshadowing the haunting, gloomy mood of the poem. The speaker’s first question to the knight is framed peculiarly. He doesn’t simply ask the knight what brings him to the lake. Instead, he says in a roundabout way, “what can ail thee” (Line 1), meaning what is wrong with the knight that he should be “alone and palely loitering” (Line 2) by the desolate lake.

The assumption that something is ailing the knight or making him sick immediately introduces the themes of illness and decay in the poem. “Palely” (Line 2) establishes the knight’s wan pallor, while “loitering” (Line 2) emphasizes his aimlessness. The dense, rich language thus establishes important themes and motifs in the opening stanza itself. The speaker also describes the knight as “knight at arms” (Line 1) for particular reasons.