The poem reads like an urgent warning about a creature the speaker never fully explains. "BIGHEAD" is named in capitals, then described in quick, jumpy lines: it has "little pointed cannibal teeth," it makes people's hair stand on end, it "comes screaming out of capture." The speaker's advice is blunt: "close the door." Yet the thing seems to reach everywhere, spying on "smiling smiling lords" and pounding on your furniture.
Because the poem never says what Bighead is, the reader has to guess. It might be a monster, a wild child, a rage, or something like madness. The title, "It Is Late," suggests that time is running short, though the poem doesn't say so directly.
The speaker sounds frightened but also oddly tender. The final address to "parents" turns the tone from alarm to sorrow: "it will break your hearts." The mood is tense and nightmarish, with real grief underneath.