The Errand
In 1840, thirteen-year-old Jessie Bollier lives with his widowed mother and sister in a cramped, single-room home in a poor district of New Orleans. His mother earns a small income by sewing dresses, while Jessie plays his fife to earn a few pennies. He dreams of becoming wealthy one day. Although he is intrigued by the lives of the slaves he sees, he is forbidden from visiting the slave market and knows little about their daily existence. His mother tells him that despite their severe poverty,

there are souls whose fates are so horrific compared to ours that we should consider ourselves among the fortunate on earth. I knew she was referring to the slaves sold daily so close to where we lived.

One day, when his mother needs to quickly sew a dress, she sends Jessie to his aunt's house to fetch candles so she can work late into the night. On his way back from this errand, two sailors who had seen him play his fife abduct him.

The Moonlight
The ship he is taken aboard is The Moonlight, heading to Africa under the command of Captain Cawthorne, a man so vicious that he bites Jessie's ear hard enough to make it bleed upon their first meeting. Captain Cawthorne informs Jessie that The Moonlight is a slave ship involved in what he calls a "lucrative and God-granted trade," and labels anyone who attempts to disrupt it as a pirate. Jessie is expected to play his fife to make the slaves "dance" once they are onboard; this exercise is meant to keep them strong and healthy so they can fetch higher prices when sold. Jessie is also required to assist with various tasks on the ship.

Onboard, Jessie meets Ned Spark, the ship's carpenter and occasional doctor, who claims to be a Christian but stands to profit from the slave voyage just like the rest of the crew, including the surly cook; Nick Spark, the Mate, who is as harsh as the captain; and Ben Stout, who expresses regret over Jessie's kidnapping, speaks kindly to him, and provides him with extra clothing and a piece of bread.

As Jessie becomes accustomed to life on the ship, he notices that Purvis, despite his coarse manners and playful teasing, is a competent sailor and is always busy. Jessie realizes that even though Purvis was one of his kidnappers, he can be trusted. Purvis informs Jessie that other ships may attempt to prevent the slave ship from completing its journey. The British, who oppose slavery, will board the ship to seize the slaves and the profits.

The Shrouds
Jessie has been bewildered by the crew's justification of the trade, as they argue that the sheer number of ships involved renders the laws against it meaningless. A crew member, Claudius Sharkey, explains to Jessie that besides British cruisers making the trade risky, American ships also patrol to catch slave importers. Nevertheless, the potential profits from these trips outweigh the risks: "He spread his arms as wide as he could to show me the money the smugglers made after they'd taken the slaves inland and sold them."

Despite Ben Stout's kindness towards him, Jessie remains distrustful and prefers Purvis: "Purvis, with his horrible coarse jokes, his bawling and cursing, Purvis, whom I trusted."

One morning at dawn, Jessie observes a sailor quietly moving forward on the ship and returning with an egg from the captain's private stash. Unsure of the sailor's identity, he later sees Purvis accused, tied up by Ben Stout and another sailor, and brutally flogged before being hung from the rigging. Eventually, Jessie discovers that Stout was the actual thief and was pleased to let Purvis take the blame. When Jessie asks Purvis why he didn't defend himself, Purvis responds, "The officers of this ship would not care what the truth was."

The Bight of Benin
As the ship nears the African coast, preparations for acquiring slaves are finalized. The crew sails up and down the coast while the captain ventures out at night in a small boat to negotiate with African chiefs selling slaves.

Jessie grows weary of life on the ship and the harsh realities of the slave trade. When Purvis requests his help in setting up a tarp to provide shade for the slaves during meals, Jessie initially refuses: "nearly senseless with rage ... I considered casting myself over the side and confounding them all!" However, he eventually complies, fearing that no one on the ship would save him and he would perish. "I went slowly toward Purvis, feeling a shame I'd never felt before," he admits.

Later, when Jessie protests against the slave trade, Purvis reacts with intense anger, reminding him that his own Irish ancestors endured similar conditions when they immigrated to America—"locked up in a hold for the whole voyage where they might have died of sickness and suffocation ... Do you know my father was haunted all his days by the memory of those who died before his eyes in that ship, and were flung into the sea? And you dare speak of my parents in the same breath with these [slaves]!"

Jessie is perplexed by how Purvis can be so outraged by the conditions his parents endured while traveling, yet remain blind to the injustice of the slaves' treatment. Jessie understands he can't discuss this with the crew; whenever he expresses distress over slavery, he is physically punished.

The slaves arrive, and two of them die. Jessie observes, "and Stout dumped their bodies over the side as I dumped waste." A little girl also perishes and is discarded in the same manner. Jessie is appalled, and when the sailors notice his reaction, he is punished, witnessed by a young slave boy who is the same age as Jessie. This shared moment creates an immediate, silent connection between them, despite the language barrier.

Nicholas Spark Walks on Water
The ship sets sail back to America. Every other day, groups of slaves are brought on deck where Jessie plays the fife while Stout whips them to make them "dance" or exercise. Jessie is filled with self-loathing, and to his horror, he realizes he resents the slaves, who represent his own bondage on the ship:

"I hated their shuffling, their howling, their very suffering!" he exclaims. "I despised the way they spat out food upon the deck, the overflowing buckets that tested all my strength ... I would have seized the rope from Spark's hand and beaten them myself! Oh, God! I wished them all dead! Just to escape hearing them! To avoid smelling them! To be ignorant of their existence!

He drops his fife on the deck and flees to his sleeping quarters, but he is dragged back and whipped by Stout for his defiance:

"But as the blows fell," he recalls, "I returned to myself. I was a thirteen-year-old boy, not as tall as, yet somewhat heavier than, a boy close to my age, now curled up in the darkness below, not a dozen yards from where I was being beaten.

The beating transforms him, heightening his awareness; he observes the sailors "with as little pity as they showed the blacks." He feels compassion for the slaves, realizing they share the same fate: all are on the ship unwillingly. He reflects, "I hated what I did [playing the fife]. I tried to console myself with the thought that, at least, it gave them time out of the hold. But what was the point of that or anything else?"

As the voyage continues, discipline breaks down; the ship becomes filthy, and the men are often drunk. Jessie distances himself from them, mentally retreating, recalling every object in his home, disconnecting from the dreadful present. During this time, he notices that the slave boy watches him each time he is on deck. He gestures to himself with the fife, saying his name: "Jessie."

When a slave attacks the mate, Nicholas Spark, Spark shoots him dead and is promptly tied with a rope and thrown into the sea. By killing the African man, Spark has eliminated the potential profit from selling him, making Spark's own life equally worthless. Purvis questions, "Don't you see? There went the profit!"

The Spaniard
At this point, both the slaves and most of the crew are ill. Stout keeps trying to befriend Jessie, who continues to ignore him. Seeking revenge, Stout takes Jessie's fife and throws it into the hold, forcing Jessie to walk over the bodies of the slaves to retrieve it—or face a flogging if he fails. A young slave boy finds the fife and gives it to Jessie, sparing him the dreadful task and punishment.

When they reach the Cuban coast, Captain Cawthorne starts negotiating with a Spaniard to sell the slaves. The next day, they will be unloaded and sold.

Ben Stout's Mistake
The sailors organize a party, bringing out rum and clothes, dressing the slaves as women, and getting drunk. Jessie is told to play his fife while the sailors dance and mistreat the slaves. A sail appears, indicating an approaching ship. Stout asserts he recognizes it and claims it poses no danger. Cawthorne, skeptical and suspecting the ship is a threat, commands that all slaves and evidence of slavery be thrown overboard. The sailors begin tossing men, women, and children over the rail. Cawthorne, thinking the ship is English, raises the American flag, only to realize too late that the ship is actually American.

The approaching ship engages in battle, which Jessie, terrified for his life, can barely perceive. Simultaneously, a storm hits both vessels. Jessie grabs the young slave boy, and they both crawl into the hold to hide. While they are down there, a sailor above closes the hatch, which is always shut during storms.

They stay trapped for several days as the storm rages. Eventually, they hear a loud crash: the ship has run aground. The hatch cover falls away, and they climb out to find everyone dead except for the dying Captain Cawthorne. The slaves are gone, and the ship is wrecked. They see land nearby and swim to it.

The Old Man
The two boys are taken in by an old man, an escaped slave living deep in the Mississippi woods. He provides them with food and helps them regain their strength. He arranges for others to take the slave boy, Ras, north to freedom. The old man instructs Jessie on how to walk the three-day journey back to New Orleans and asks him to keep his existence a secret to avoid being captured and returned to slavery.

Home and After
Jessie returns home and reunites with his mother and sister, but he struggles to adjust to his former life. His previous ambitions of becoming wealthy have vanished, as he wants nothing to do with anything linked to slavery. He realizes that "everything I considered bore, somewhere along the way, the imprint of black hands." Eventually, he chooses to become an apothecary—the 1840s version of a pharmacist—and relocates to Rhode Island, where there are no slaves. He sends for his mother and sister and leads a quiet life. He misses the South and spends the rest of his life wondering about Ras's fate, but he never learns what happened. When the Civil War begins, he joins the Northern forces.

Over time, the terror of the voyage fades from his memory, and he no longer thinks about it daily. He marries and starts a family. However, one thing from the voyage remains: he cannot bear the sound of music because it reminds him of the slaves dancing:

For at the first note of a tune or a song, I would see once again as though they'd never ceased their dancing in my mind, black men and women and children lifting their tormented limbs in time to a reedy martial air, the dust rising from their joyless thumping, the sound of the fife finally drowned beneath the clanging of their chains.