The story begins as the narrator, one of two survivors stranded in the belly of a whale, explains to his companion how (unknown to the companion) their lives were interwoven.

The narrator details how, when he was three, his widowed mother fell in love with the companion — then an eighteen-year-old roustabout — who was charming at first but was later revealed as a gambler and womanizer. The roustabout then disappeared, leaving only his gambling debts and the mother sick with consumption. The magistrate repossessed their estate to pay for the debts and the mother later died, leaving the boy an orphan. On her deathbed, the boy's mother instructs the boy to avenge her death, telling him:

"Find him, bind him, tie him to a pole and break his fingers to splinters. Drag him to a hole until he wakes up, naked, clawing at the ceiling of his grave."

Fifteen years later, having found work cleaning a priory, the boy hears of a whaler captain who matches the roustabout's description and is known for "wanton cruelty". The next day he joins a privateer ship to hunt him down. After 20 months at sea, the privateer crew spots the whaling ship, but a giant whale attacks both ships before they are able to board. Everyone is killed, except the narrator and the roustabout.

The narrator then tells the man who ruined his mother's life that it must have been by "providence" that only they survived, and cautions the roustabout to listen closely, as what he will be told next "will be the last words (he) will hear". Though the lyrics end here, the musical theme representing the mother's instructions is repeated several times in escalating tempo, implying the culmination of the narrator's pyrrhic victory over the roustabout.

"The Mariner's Revenge Song" has been one of the Decemberists' most popular at live performances. It had been played at virtually every live show as an encore since its release until the 2006 tour. At this point, the band swore off playing it at nearly all of the shows, saying that they were giving it a break for a while.

When played live, the song utilizes a characteristic variety of instruments, with Chris Funk on mandolin, Nate Query on stand-up bass and bowed bass, Colin Meloy on vocals and guitar, John Moen on floor tom and Jenny Conlee on accordion. The band usually brings out a large paper maché whale jaw to use as a prop, and encourage the audience to "scream like you're being swallowed by a whale" during the part of the song when the whale attacks the ship.

...
Wikipedia