Despite its title, the jail in this poem isn't a building. It's the speaker's own head. The poem opens with exhaustion and a bed that offers no comfort, because sleep brings nightmares. Siblings sleeping calmly nearby sharpen the loneliness: everyone else rests, and the speaker can only envy them. When morning comes, the nightmares leave nothing behind except a pounding heart, sweat, and tears.
The middle of the poem makes its central move with three short lines: the brain is the jailer, the skull is the cell, and thoughts are the punishment. There's no escape because the thing trapping the speaker is also the thing doing the thinking. The tired tone then shifts from physical to emotional weariness. The final lines, "I am done with the lies, / I am done with the pain," build toward an uncertain, bleak ending: "I don't know what to fight for." The mood is heavy, raw, and hopeless, and the plain, short lines make it feel honest and unguarded.