The first line of the poem merely contains the subject, rather than an independent clause. This is conveyed through the perspective of a third person, objective speaker. The poem is about “The little boy” (Line 1). The use of the determiner “The” implies that it is not just any boy the speaker refers to; rather, this is a specific boy: a boy who is “lost” (Line 1). “Lost” here serves not as a verb, but as the beginning of a participial phrase (the past participle of a verb and any other words or phrases that modify it). Participial phrases can function as adjectives describing a noun. “Lost in the lonely fen” is therefore the participial phrase modifying “boy” (Line 1). A “fen” is a swamp, marshland, or wetland—not the typical setting one would expect a child to be wandering in alone. The adjective “lonely” heightens the desolate tone conveyed in the first line.

Readers discover in the second line why the boy is “lost” (Line 1). He has been “led,” which implies that he was guided by some force or power rather than making his way with his own agency.