We meet our "hero," a boy named Eustace Clarence Scrubb. He's so unpleasant that the narrator tells us he almost deserves this awful name.
Eustace's parents are extremely progressive – they have Eustace call them by their first names, they don't eat meat, drink alcohol, or smoke tobacco, and they love fresh air.
Eustace himself is pompous and unimaginative. He only likes books if they're nonfiction and he only likes animals if they're dead and classified as specimens.
Eustace's cousins are Peter, Susan, Edmund, and Lucy, four siblings who have been to the magical land of Narnia twice before (in the books The Lion, the Witch, and the Wardrobe and Prince Caspian). Eustace doesn't like them, but he does like bullying and teasing them.
One summer Edmund and Lucy come to stay with their Aunt Alberta and Uncle Harold, Eustace's parents. Their own parents have gone to America, taking their sister Susan with them, and their brother Peter is staying with Professor Kirke, a family friend (the same Professor who was in The Lion, the Witch, and the Wardrobe).
One day while they are staying at Eustace's house, Edmund and Lucy begin talking about their adventures in Narnia. They wonder when and how they will get to go back to that magical land.
As they talk, Edmund and Lucy look at a portrait of a sailing ship hanging on the wall of Lucy's bedroom. The ship is shaped to look like a dragon and painted green with a purple sail, and they think it looks Narnian in style.
Eustace, who has been eavesdropping, comes in and starts teasing Edmund and Lucy. Because he doesn't believe in Narnia, he thinks they're just playing a game.
Eustace starts composing a rude poem about Edmund and Lucy. Edmund is rude to Eustace and tries to make him go away.
Ignoring Edmund, Eustace starts an argument with Lucy about the picture. He asks if she likes it, and she says she does. He says it's a terrible picture and asks her to defend her opinion.
Lucy says she likes the picture because it seems so real – she can almost smell the ocean breeze and see the waves rolling and the ship moving on the water. Before Eustace can tell her she's wrong, he looks at the portrait and it does seem like the water is real.
As Eustace begins to feel slightly seasick, the world of the picture comes more and more to life. The ship is really moving, the waves are really splashing, and the sea breeze starts to blow through Lucy's bedroom.
Eustace thinks Edmund and Lucy are playing a practical joke on him and demands they stop.
All three of the children are suddenly hit by a cold splash of water coming out of the picture frame.
Eustace tries to smash the picture. Edmund tries to stop him. Lucy also grabs on to Eustace. All three of them are dragged toward the picture.
There is a confusion of sizes – either they have shrunk or the picture has grown – and they find themselves standing on the picture frame looking down into the sea. Eustace panics and grabs at Edmund and Lucy, and they all tumble down into the water.
As she hits the water, Lucy stays calm. She kicks off her shoes, keeps her mouth closed and her eyes open, and swims. Then Eustace clutches at her and they go under.
Lucy surfaces to find Edmund treading water and holding Eustace. The people on the ship are arranging to bring all three of them on board. Lucy sees a familiar face above her on the deck of the ship but doesn't recognize the person at first.
With Edmund's help, the familiar person ties ropes to Lucy and eventually she is hauled aboard. Next Edmund and then Eustace are hauled up, too.
As she reaches the deck of the ship, Lucy recognizes the familiar face – it's King Caspian of Narnia, whom she met in a previous adventure (described in the book Prince Caspian). Lucy, Edmund, and Caspian have a happy reunion.
Caspian is introduced to Eustace, who is crying and asking to go back. But there is nowhere he can go back to – the gateway to the "regular" world has disappeared, and there's no sign of the picture frame or Lucy's bedroom. In a combination of fear and seasickness, Eustace throws up.
Caspian orders spiced wine and Edmund, Lucy, and Eustace drink it. For Edmund and Lucy, it hits the spot. Eustace throws up again and cries and asks for "Plumptree's Vitaminised Nerve Food." We don't know exactly what that is, but think of a protein shake mixed with cough syrup and you'll probably get the idea. (Note: Shmoop does not recommend this as a cocktail recipe.)
Reepicheep, the two-foot-tall talking mouse that Lucy and Edmund met on their last visit to Narnia, appears. Eustace, thinking the Mouse is a performing animal, demands that he be taken away.
Reepicheep greets Edmund and Lucy and asks if Eustace is under their protection. Just when it looks like there might be a fight, Edmund and Lucy both sneeze, and Caspian arranges for all three children to go below and change into dry clothes.
Caspian gives his cabin on the ship to Lucy. Lucy adores the cabin, which is small and snug but richly decorated and has three windows looking out onto the water.
Lucy changes into some of Caspian's clothes; she has to go barefoot because none of his shoes will fit her. She feels excited about the sea voyage and thrilled to be back in Narnia.