The Last Mapmaker (2022) is a middle grade fantasy adventure novel written by Christina Soontornvat. Through folklore, monomyth archetypes, and a cast of characters who are not quite what they seem to be, the novel explores the impacts of imperialism, social inequality, and self-deception. The Last Mapmaker is one of Soontornvat’s three Newbery Honor Books. It was also named a New York Times Best Children’s Book of the Year, a Kirkus Best Book of the Year, and an AudioFile Best Audiobook of the Year, among other literary honors.

This guide uses the e-book edition of the text published in 2022 by Candlewick Press. (Pagination may differ from print editions.)

Content Warning: Both the source text and this guide contain descriptions of social inequality, parental negligence, and the impacts of colonialism and imperialist exploitation.

Plot Summary

The Last Mapmaker tells the story of Sai Arawan, a 12-year-old girl in the Thai-inspired fantasy kingdom of Mangkon. She works as an assistant for Paiyoon Wongyai, the kingdom’s Master Mapmaker. Although she pretends to come from a respectable family of means, Sai actually lives in poverty with her father, Mud, who makes a dubious living as a con artist and has an alcohol addiction. In Mangkon society, a person’s family background is crucial to determining social and economic status; this information is displayed by adornments called lineals. If anyone knew the truth of Sai’s background, she would be considered a nobody and would have no opportunities to change her circumstances.

After conquering and colonizing its island neighbors, Mangkon recently declared the end of a war which had lasted more than 20 years. Now, the Queen is sending four ships to sea with the mission of discovering and charting new territories for her to claim. Paiyoon is desperate to join the voyage, but old age and arthritis have made his mapmaking abilities. When he sees Sai’s skill at forgery, he invites her to join the voyage and secretly draw the maps in his name. Sai leaps at the chance to get away from Mud and the city of An Lung, and she plans never to return.

One day, Mud learns that Sai has lied to him about where she works. He finds her key to the mapmaker’s shop, but she won’t tell him what the key unlocks because she knows that he’ll only rob the place. As punishment, Mud refuses to let Sai leave their apartment until she tells him. Desperate not to miss the voyage, Sai gives Mud her entire savings so that he will let her go. Although she successfully escapes her father’s grasp, she sets sail aboard the Prosperity without any funds to build a new life.

The Prosperity’s commander is Captain Anchalee Sangra, a revered war hero and great-niece to the Queen. Miss Rian Prasomsap, a stylish young woman said to be close friends with the captain, is also on board. To Sai’s surprise, so is Grebe, a boy who once tried to rob her back home. She knows that if he recognizes her, he will have the power to expose her secrets and ruin everything, so she avoids him by remaining in her cabin as much as possible. However, she does finds a friend and a role model in Rian, who also came from a low-class background but found a way to rise above it. Sai is eager to follow in Rian’s footsteps.

Soon after the Prosperity docks at Pitaya for a day, Sai finds a stowaway from the island on board the ship. When the boy—whose name is Bo—learns that the ship isn’t headed for An Lung as he thought, Sai agrees to help him stay hidden rather than turning him in. Meanwhile, Rian tells Sai that the real purpose of the expedition is to find the Sunderlands, a Great Southern Continent believed by many to be merely a fairy tale. According to legend, dragons that once lived near Mangkon now inhabit the Sunderlands on the far side of the perilous Harbinger Sea. Captain Sangra doesn’t want to take the risk of searching for the Sunderlands, and Paiyoon insists that it doesn’t exist. However, Rian believes that it does, and she believes that Paiyoon can persuade the captain to seek them out. She urges Sai to convince Paiyoon that the Sunderlands are worth looking for. The reward, she says, is a Lineal of Honor from the Queen that will allow Sai to achieve all her dreams.

With Bo’s help, Sai secretly searches Paiyoon’s trove of sailor’s logs, looking for evidence of the Sunderlands. Rian contributes a rare fishermen’s map showing more detail of the southern landmass than any Sai has yet seen. Sai comes to realize, however, that Paiyoon knows the Sunderlands exists and is purposefully steering the Prosperity away from it. Because Paiyoon won’t change his mind, Rian convinces Sai to forge a letter from the captain—who has recently become gravely ill—ordering that Paiyoon be dismissed from his duties. As a result, he is forced off the ship at the next port, and Sai is declared the new mapmaker. Through another forged order, Rian gains command of the ship until the captain recovers.

At the edge of the Harbinger Sea, a massive storm nearly destroys the Prosperity. During the chaos caused by the storm, Captain Sangra seizes the opportunity to tell Sai that Rian has been poisoning her and that everything Rian has told Sai about herself is a lie. Sangra also reveals that she fell in love with a commoner and had a son with him. The man died, and now she is trying desperately to reunite with her son. Putting together several different clues, Sai deduces that Bo is the captain’s son.

While the storm is still raging, Sai witnesses Rian push Captain Sangra overboard. The rest of the crew fears being charged with mutiny unless they all stick to the same story. Grebe tells Sai that the crew plans to kill her because they think she will betray them. She that learns Grebe actually wants to help her escape in order to repay a debt of kindness that he owes to her father. With Grebe’s help, Sai and Bo escape from the ship and ride a floating crate to a tiny nearby island. From there, they make their way to the Sunderlands, guided by Rian’s map and a living dragon.

The Sunderlands are beautiful, lush, and rich in natural resources. They are also home to the dragon and her four eggs. While Sai and Bo explore the island, they encounter Rian. She says the Prosperity went the wrong way at first but turned back. The rest of the crew is still on the ship, which has run aground. Sai confronts Rian about pushing Captain Sangra overboard. When Rian realizes that Sai doesn’t believe her lies, she tries to push Sai off a cliff. Fortunately, Bo saves Sai by tackling Rian and holding her at spearpoint. Sai and Bo reveal the truth about Rian to the other crewmembers, who lock her in the brig.

As soon as the Prosperity is repaired, they sail home to Mangkon, where they learn that Captain Sangra survived and was rescued by Paiyoon. After disembarking from the Prosperity, he chartered a boat to follow the ship, suspecting that Sai might need help. Now, Sangra is reunited with her son Bo and begins campaigning for reforms to Mangkon’s class system. While Rian awaits trial for mutiny and attempted murder, word of Sai’s discoveries spread. In order to deter profit-seekers from exploiting the Sunderlands, Sai offers an altered version of the truth—one in which the area is portrayed as a barren wasteland. Sai also opts to accept a cash prize from the Queen rather than the Lineal of Honor, for she has realized that society’s values do not define her worth. She becomes Paiyoon’s apprentice, rather than his assistant, and takes on the title of Mapmaker-in-Training.