The poem opens with the imagery of a body swaying from the beam where it was hanged by the rule of law. The letter of the law being carried out here is portrayed as a shadow cast upon the greenery of the Shenandoah Valley in the slave-owning state of Virginia where the execution took place. The implicit suggestion here is that while Brown may been rightfully executed for breaking the law, the letter of the law allowing people to own other human beings casts a far darker shadow upon Virginia than any trespass of its law Brown committed.
The body belongs to John Brown, a cut received on the head of the zealous abolitionist helping to identify him when captured. The wound is one of many he received in his violent efforts to draw attention to the evil of the institution as well as help individual slaves escape bondage. This final would will be the one that never heals.
What also will never heal is the anguish that John Brown felt about the existence of slavery, a fact eternally marking his face beneath the execution hood pulled over his head. The hood is then transformed into a symbolic veil used in an attempt to hide from view the horrible future in store for supporters of slavery.
The anguish of his face which reminds the South of their transgression against nature regardless of any law that denies its existence is successfully covered by the hood, but not the famous long streaming beard. The long, overgrown beard that gave the fiery abolitionist the nickname Weird John Brown. It was the beard (famous portrayed in drawings, but grown by Brown only during the last year of his life as he prepared his series of raids) that solidified his reputation among most opponent and some supporters of his mental instability.
The poem concludes with a metaphor that fiery integrity and perhaps slightly mad zeal to correct the wrongs of a nation. “The Portent” is the poem which opens Melville’s collection of Civil War poetry Battle-Pieces and thus situates the violence, madness, shame, anguish and righteous inevitability within John Brown as the “meteor of the war.”