La historia se inicia con un narrador sin nombre que relata una travesía marina estival desde Charleston (Carolina del Sur) a Nueva York a bordo de buque Independence. El narrador, mediante la lista de pasajeros, se entera que su ex compañero de universidad Cornelius Wyatt se encuentra a bordo de la embarcación junto a su mujer y las hermanas de ésta, aunque ha reservado tres cabinas. Después de conjeturar que la habitación adicional era para un sirviente o para equipaje extra, se da cuenta que su amigo ha comprado a bordo una caja de pino oblonga en la que, primeramente, piensa que Wyatt oculta valiosas pinturas para vender en Nueva York. Avanzada la historia, el narrador descubre que la esposa de su amigo había muerto un día antes de abordar y la llevaba en la caja, además, las mujeres que se encontraban con él eran sus sirvientas.
The story opens with the unnamed narrator recounting a summer sea voyage from Charleston, South Carolina to New York City aboard the ship Independence. The narrator learns that his old college friend Cornelius Wyatt is aboard with his wife and two sisters, though he has reserved three state-rooms. After conjecturing the extra room was for a servant or extra baggage, he learns his friend has brought on board an oblong pine box: "It was about six feet in length by two and a half in breadth." The narrator notes its peculiar shape and especially an odd odor coming from it. Even so, he presumes his friend has acquired an especially valuable copy of The Last Supper.
The box, the narrator is surprised to learn, shares the state-room with Wyatt and his wife, while the second room is shared by the two sisters. However, for several nights, the narrator witnesses his friend's surprisingly unattractive wife leaving the state-room every night around 11 o'clock and going into the third state-room before returning first thing in the morning. While she is gone, the narrator believes he hears his friend opening the box and sobbing, which he attributes to "artistic enthusiasm."
