Tress of the Emerald Sea (2023) is a fantasy novel by Brandon Sanderson, set on one of the worlds of Sanderson’s fictional universe, Cosmere. The novel tells the story of Tress, a girl content with her life on a small island, and her journey to save Charlie, the man she loves, from the Sorceress.

This guide uses the 2023 Dragonsteel Entertainment, LLC edition.

Plot Summary

Tress’s life on the Rock, an island on the planet Lumar, is a simple one. She washes windows and helps her family with shopping and cooking. The most exciting part of her life is the joy she finds in collecting cups that sailors bring from around the world. The seas of Lumar are composed of aether spores, which behave similarly to water, but the spores are dangerous, so the sailors who travel these seas represent an unknown world of adventure to Tress.

When she washes the windows of the duke’s home, she chats with Charlie. Charlie is the duke’s son, but he pretends (badly) that he is a gardener because he does not want Tress to judge him. This dynamic defines their playful relationship –Charlie lying quite badly, and Tress going along with it.

The duke takes his family away on a mission to find a princess for Charlie to marry. Charlie admits to Tress that he likes her and promises to bore every princess until he can come back. He vows to send her a cup from every port where he is a successful bore. After five cups, the messages from Charlie stop. When the duke and his family return, Charlie is no longer with them; the duke announces that there was an unfortunate accident, and he has adopted his nephew as his heir. Tress discovers from servants that the duke discovered Charlie’s attempts to scare away princesses and sent him to the Sorceress—the duke and the king claimed to make an alliance with the Sorceress, but Tress realizes that they did it to get Charlie out of the way.

Tress is determined to save Charlie, but doing so involves illegally leaving the Rock. Her parents and some of their friends help Tress sneak on board a merchant ship, but it turns out to be a smuggler’s ship. They imprison her, but when another ship attacks, and the spore sea hardens and becomes walkable for a time, Tress takes the opportunity to jump out of an opening created by a cannonball and walks to the enemy ship, hoping it is one of the king’s. Tress takes with her Huck, a talking rat who was also imprisoned on the smuggler’s ship.

The other ship, the Crow’s Song, turns out to be a recently-turned pirate ship, a transition initiated by Captain Crow. Tress keeps herself on the ship and alive by washing the deck, showing her usefulness. Observing and speaking with the crew, Tress suspects that the majority of the crew have been tricked into becoming deadrunners, or pirates who actually kill others, and that Captain Crow and Laggart, the cannonmaster, are behind it. The crew clearly fears Crow. Tress has an opportunity to escape the ship at the next port, but she chooses not to abandon the crew, hoping to help free them from Crow’s control.

To stay on the ship, Tress agrees to become the ship’s sprouter, which means she has to handle and experiment with spores, the material that pours from the planets’ moons and composes the seas. This job includes using roseite spores to close holes in the ship’s hull. The more exposure Tress gains to different kinds of spores, the less she fears them.

Tress discovers that the previous sprouter had hidden away midnight spores, considered the most dangerous of all. He had acquired them from Hoid, the ship’s cursed cabin boy and, in his un-cursed state, narrator of the novel. Tress learns about the spores from Ulaam, the ship’s doctor. She experiments with them and uses some to create a small enough midnight creature to spy on Captain Crow. Tress learns that Crow wants to find Xisis, the dragon in the Crimson Sea, so she can be healed from being a spore eater, one who is a living host for spores and will die within a year. Tress shares this knowledge with Ulaam and discovers that the dragon requires an enslaved human as trade for healing, and Tress realizes that Crow means to trade her.

Tress’s mission now aligns somewhat with Crow’s, since she has to go through the Crimson Sea to get to the Midnight Sea, where the Sorceress lives. She convinces the crew, who believe she is a spy for the king, to agree to Crow’s desire to sail to the Crimson Sea. Along the way, she plots ways to capture Crow without triggering the vines that protect Crow. Tress examines the previous sprouter’s schematics for cannons, learning how to use spores for weapons and other technology, and uses them to invent something of her own: a flare gun that will activate vines to trap Crow but not threaten her in a way that would activate her own vines.

Crow discovers Tress and the other crew members’ plan. Crow overpowers them and then takes Tress as her hostage to see Xisis under the sea. In the dragon’s lair, Tress considers the hint Hoid gave her through his curse: that she has everything she needs. So, after Crow offers Tress to the dragon, Tress offers Crow to the dragon, initiating a debate over whom the dragon should take.

Xisis finally agrees with Tress and takes Crow, admitting that if Crow left his lair, her cure would not last more than a year, anyway. He sends Tress away with the three boons she asks for on behalf of her friends among the crew, since he says he cannot help with her quest. Tress returns to the Crow’s Song, and the crew insists on helping her find Charlie, even when they discover that Huck had sabotaged the food to try to force Tress to stop pursuing the Sorceress.

Tress hopes to lure one of the Midnight Sea monsters guarding the Sorceress’s domain into her own control; her attempt fails, but Huck suddenly commands the monster to take them to the Sorceress. He refuses to answer Tress’s questions as they sail to the Sorceress’s island. In the tower, the Sorceress claims Tress can take Charlie away if she gives up the two cups she is holding. Tress agrees, but before they leave, she realizes something is wrong with Charlie. She runs back to the Sorceress to confront her, realizing that Huck is actually a cursed Charlie, forbidden from speaking of his curse.

The Sorceress is about to curse Tress when her alarms go off and all three of them see the Crow’s Song on her security footage; the crew had decided to go after Tress when she told them to wait on the edge of the Midnight Sea. They use Tress’s invention in the cannons to trap the metal monsters guarding the tower, and Charlie lets them into the tower. Tress realizes that part of breaking Hoid’s curse involves getting him to the tower, and she knows that for some reason, he is the only one who can defeat the Sorceress. The crew gets Hoid to the tower, where his curse has lifted, his mental health returned, and he protects Tress, Charlie, and the crew from the Sorceress.

Before the crew leaves, Tress demands that the Sorceress leave their world; at Hoid’s threatening, she agrees. Hoid cannot lift Charlie’s curse, but he alters the terms so that Charlie will become human again when they return to the Rock. As payment for defeating the Sorceress, the king gives Tress and the crew a new ship and allows residents of the Rock to leave, offering instead a generous payment if they work 20 years there.

Tress’s family joins her and Charlie on the ship, and they all set back out on the sea.