Neverseen (keeper of the Lost Cities, #4)

The fourth installment in Shannon Messenger's middle-grade fantasy series follows Sophie Foster, a teenage girl created by the Black Swan, a secret organization that genetically modified her to possess extraordinary abilities including telepathy, teleportation, and the power to inflict emotions. Sophie lives among elves in hidden cities, having been raised by a human family before being brought to the elvin world. In previous books, Sophie discovered that a rebel group called the Neverseen, allied with the ogres, threatens elvin stability, while the ruling Council remains too focused on maintaining order to confront the real danger.

The story opens as Sophie and her friends Fitz, Keefe, Biana, and Dex flee the Lost Cities before the Council can punish them for laws broken during a failed ambush of the Neverseen. They remove their registry pendants, tracking devices issued by the Council. Before they leave, Councillor Oralie secretly gives Sophie a cache belonging to the late Councillor Kenric, a glass marble containing dangerous forgotten secrets that Sophie must keep hidden. Sophie teleports the group to Florence, Italy, where they follow a series of riddles to meet Mr. Forkle, the only Black Swan member Sophie knows.

Mr. Forkle leads them to Alluveterre, an enormous underground cavern serving as the Black Swan's hidden base. Della, Fitz and Biana's mother, stows away using her Vanisher ability to turn invisible. Sophie meets the Collective, the Black Swan's five disguised leaders, including Granite, a crystallized Telepath who becomes Sophie's telepathy trainer. The Collective plans to rescue Prentice, a Black Swan member imprisoned in Exile, the elves' maximum-security prison, whose mind was broken thirteen years earlier to protect Sophie. Mr. Forkle restores a stolen memory to Sophie: As a five-year-old, she saw a mysterious elvin boy whose face was blurred by a device called an addler. Mr. Forkle believes this "Boy Who Disappeared" attended Exillium, a dreaded school for banished elves.

Sophie and Fitz begin training as Cognates, an extremely rare telepathic partnership requiring complete trust. Meanwhile, Keefe, an Empath who senses emotions, struggles with the revelation that his mother, Lady Gisela, is a Neverseen leader. His grief deepens when scouts report Lady Gisela was likely killed by fellow Neverseen members. A mysterious plague also begins spreading through the Neutral Territories, lands between the major powers, sickening gnomes and killing plant life. Sophie, Biana, and the gnome Calla investigate Brackendale, where they confront a Neverseen Psionipath who creates force fields. The Black Swan also interrogates their prisoner Gethen; though the ruse fails, Mr. Forkle extracts useful intelligence by dividing his consciousness.

The Collective leads the group to break Prentice out of Exile, but the mission is a trap: All twelve Councillors are waiting. Fitz is impaled by the venomous antenna of a giant arthropleura, a massive centipede-like creature, and nearly dies. Sophie uses Kenric's cache as leverage, negotiating the group's release, Prentice's freedom, and full pardons in exchange for volunteering her group for Exillium. Her adoptive mother Edaline later hides the cache in the void, the space between dimensions, and establishes a one-use emergency verbal command to summon it. When Sophie enters Prentice's mind, however, she finds absolute emptiness: His consciousness has retreated beyond her reach.

At Exillium, students wear masks and hoods under Coaches who enforce anonymity through fear. Sophie encounters Tam Song, a Shade with shadow-based abilities, and his twin sister Linh, a Hydrokinetic who controls water. The twins have lived near the former Wildwood Colony, where the plague originated, and Tam overheard Councillors admitting they should have warned the gnomes about the threat.

Dex builds a device called the Twiggler to hack a secret archive in Lumenaria and discovers that the ogres possess drakostomes, microscopic parasitic nematodes preserved in the bark of the Panakes, legendary gnomish healing trees. The ogres destroyed these trees five thousand years ago when they conquered the gnomish homeland and used the parasites as leverage for favorable treaty terms. The Council kept the threat secret at the dying gnomish leaders' request. When Calla learns the truth, she spreads it to the gnomish community, sparking a massive protest in Eternalia, the elvin capital.

During the Council's public address, Fintan, a Pyrokinetic everyone believed dead, appears alive wielding Everblaze, a dangerous fire nearly impossible to extinguish. King Dimitar, the ogre king, emerges alongside him. Fintan offers the gnomes a choice: Submit to servitude in Ravagog, the ogre capital, in exchange for the cure, or face the plague's continued spread. He gives them one week.

Sophie and her friends infiltrate Ravagog, joined by Tam, Linh, Calla, and Alvar, Fitz and Biana's older brother who has visited the city as a Council Emissary. Calla opens a secret tunnel using the roots of the Four Seasons Tree, the transformed remains of ancient gnomish leaders, since gnomes become trees when they die. Inside, Keefe distracts King Dimitar while Sophie and Fitz use their Cognate abilities to probe the king's mind. They discover the cure is a hoax: The silver chest is designed to unleash the plague in the Lost Cities.

Chaos erupts when Biana is caught trying to steal the chest. Linh unleashes a tidal wave that destroys the city's bridge and smashes its gates, carrying the group to safety. Near Wildwood, Brant, a Neverseen Pyrokinetic, and Fintan trap them with walls of Everblaze. Fintan reveals that Alvar has been a Neverseen member all along and is the Boy Who Disappeared. Alvar confirms his betrayal, admitting he helped plan Sophie and Dex's kidnapping. Sophie uses her Black Swan pendant to ignite uncontrollable white fire that breaches the Everblaze wall, and Calla launches them skyward before Sophie teleports the group to safety.

Back at Havenfield, Sophie's home with her adoptive parents Grady and Edaline, the Vacker family reels from Alvar's betrayal. Calla reveals the Panakes' true nature: They were gnomes who sacrificed themselves, their life energy creating healing blossoms. She announces she has begun an irreversible transformation into a Panakes tree, the only real cure. Despite Sophie's pleas, Calla chooses a hill at Havenfield. By morning, a magnificent tree stands with millions of color-shifting blossoms that provide the cure. The Council offers the gnomes the choice to stay or leave; they unanimously remain but demand no more secrets.

In the final chapters, Keefe gives Sophie a necklace of hand-painted beads and acts evasive. Sophie follows him to the Lake of Blood in the Neutral Territories and discovers he has met Fintan, Brant, and Alvar. Keefe trades Kenric's cache to the Neverseen by mimicking Sophie's voice to trigger the emergency command that summons it from the void. When ordered to brand Sophie to prove his loyalty, Keefe instead activates a crystal hidden in the necklace, sending her to safety on a beam of light. He remains with the Neverseen.

Sophie returns devastated. Mr. Forkle and Granite reveal their identities: Mr. Forkle is Magnate Leto, principal of Foxfire, the elvin academy, and Granite is Sir Tiergan, Sophie's telepathy Mentor. Both have secretly protected her throughout her time in the Lost Cities. Mr. Forkle offers one hopeful note: Thanks to Tam's shadow ability, Prentice is finally awake.