Flashback

The seventh installment in the Keeper of the Lost Cities series, Flashback follows Sophie Foster, a human-raised elf genetically engineered by a secret organization called the Black Swan, as she and her friends recover from a devastating attack, confront old enemies, and face revelations that reshape their alliances and relationships.

Sophie attends a sentencing hearing for Alvar Vacker, the traitorous eldest son of the prestigious Vacker family and a former member of the Neverseen, a rebel organization. Every Telepath who has searched Alvar's mind confirms his memories were completely erased, and Sophie privately questions whether punishing someone who cannot remember his crimes is fair. The twelve-member elvin Council announces a controversial decision: rather than sentencing Alvar to life in prison, they will place him under six-month observation at Everglen, the Vacker family estate, monitored by goblin guards and a tracking device called the Warden, built by Sophie's best friend Dex Dizznee. Fitz Vacker, Alvar's younger brother, accuses his parents Alden and Della of secretly authorizing the arrangement. He removes his home crystal, a jewel keyed to Everglen that allows him to travel there, and declares he is moving out.

Fallon Vacker, a reclusive Ancient (elves who have lived for thousands of years) and founding Councillor, interrupts to warn that the property was originally chosen by his sister Luzia Vacker, a Flasher with light-manipulation abilities who helped create the illusions hiding elvin cities. Sophie suspects Luzia is concealing something about Everglen's history, particularly regarding Luzia's past work with the imprisoned villain Vespera.

Sophie finds Fitz training in a remote desert arena with his goblin bodyguard Grizel and convinces him to return to Everglen to search for hidden secrets. Fitz agrees on the condition that they resume Cognate training, a telepathic partnership requiring total honesty. This terrifies Sophie because she has been hiding a crush on Fitz.

Three Neverseen members ambush them: Gethen, a Telepath; Ruy, a Psionipath who generates force fields; and Umber, a Shade who manipulates shadow-based power. Umber attacks with shadowflux, a sixth elemental force distinct from normal shadows, piercing Fitz's chest and shattering bones in Sophie's right hand. Dex arrives with Wylie Endal, a Flasher and Sophie's ally, after Sophie activates her panic-switch ring. Wylie fights using his Flasher abilities, and the collision between his light and Umber's shadowflux creates an explosion that disables the force fields, forcing the Neverseen to flee. During the attack, the Neverseen reveal that caches Sophie's friend Keefe Sencen stole from them are fakes. Keefe later realizes a pendant he gave Sophie was contaminated with ethreium, an ogre tracking enzyme, explaining how the Neverseen tracked her.

Sophie and Fitz are treated at the Healing Center at Foxfire Academy by the school physician Elwin. Tam, a Shade and Sophie's friend, removes the shadowflux from their bloodstreams, but his mentor Lady Zillah identifies residual echoes that build a bridge between fear and pain. Whenever Sophie has nightmares, the echoes trigger physical agony in her hand and head. She comes to think of this phenomenon as a monster in her mind. Fitz's echo, near his heart, causes his ribs to refracture with strong emotions, keeping him sedated for over two weeks.

Sandor, Sophie's goblin bodyguard, assembles a multispecies protection team: Flori the gnome, Bo the ogre (a Mercadir, an elite warrior class), Tarina the troll, and Nubiti the dwarf. Bo is revealed to be the arranged spouse of Ro, Keefe's ogre bodyguard, assigned by King Dimitar to keep Ro safe. Tarina privately proposes an alliance between Sophie and Empress Pernille, warning that threats are spreading beyond the elvin world. Mr. Forkle, Sophie's mentor and a Black Swan leader, brings Sophie and Dex to meet Tinker, the organization's reclusive Technopath, an elf with technology-related abilities. Tinker provides gadgets including fingernail devices that control Sophie's enhancing ability and a null pin that blocks technological tracking. Sophie begins intensive combat training with her bodyguards.

Sophie, Fitz, and Keefe work to recover memories that Lady Gisela, Keefe's mother and the Neverseen's current leader, erased from Keefe's mind. Using enhanced Cognate power, Sophie and Fitz uncover a fragmented memory of Lady Gisela sending young Keefe to London to deliver a sealed letter to a house with a green door. Their telepathy mentor Tiergan determines that some memories were deliberately shattered beyond recovery. Meanwhile, Flori discovers that the rhythm of Sophie's echoes matches that of vesperlace, a vine that grows in darkness, and begins composing a healing song rooted in the music of dark-dwelling plants.

Sophie and Fitz's relationship deepens through nightly telepathic conversations. Mr. Forkle arranges a meeting with Fintan, the imprisoned former Neverseen leader, who warns that Vespera is planning something for the Celestial Festival involving Luzia Vacker and intends to expose the truth behind the Vacker legacy. Fintan confirms that Lady Gisela's London errand involved recruiting a human. In exchange, Fintan demands Sophie bring Marella, a friend who has secretly manifested pyrokinetic abilities (fire manipulation banned in the Lost Cities, the hidden elvin world), to train with him. Sophie refuses but takes the warning seriously.

At Everglen, Fitz tells Sophie he wants her on his match lists (the compatibility rankings used in elvin matchmaking), and Sophie admits she has liked him since they first met. Before they can say anything more, Silveny's panicked transmissions interrupt them. Silveny, a winged unicorn called an alicorn, is in premature labor with twins. Tarina offers to save the babies using troll transport pods where premature young can finish developing, but only if Sophie formally commits to the alliance with Empress Pernille. Sophie agrees. The newborns are implanted in a hive, and Luzia's secret is revealed: She has been allied with the trolls for thousands of years, hiding their hive first at Everglen and later at her own property, Dawnheath. Days later, Sophie and Fitz acknowledge their mutual feelings and agree to take things slowly. Keefe, who sensed the emotional shift as an Empath, insists the change does not affect their friendship.

The group uses the Celestial Festival as a trap, creating layered illusions at the festival site while patrolling in disguise. Marella decides to accept Fintan's training, and Flori completes her healing song, which fades Sophie's echoes, though Lady Zillah warns a small remnant will always remain like scar tissue. On festival night, Fitz monitors the Warden tracker and sees Alvar approaching Everglen's back gate. Sophie teleports everyone to the estate, where they discover the Neverseen were broadcasting illusions using mirrors rather than being physically present. Vespera's voice triggers Alvar's total memory restoration, and he reverts to his old allegiances. Vespera shatters an illusion-concealing orb, revealing a hidden experimental troll hive at Everglen. Seven mutant troll newborns, massive and bloodthirsty, escape into the clearing. Umber is crushed and killed by the falling hive door. Tam disables Ruy's force fields with shadowflux, and Sophie's allies fight the newborns, discovering the creatures can only be killed by their own fangs. Sandor and the other warriors take down all seven.

Sophie, Keefe, Tam, and Ro teleport to the alicorn baby hive after Silveny sends desperate transmissions. Lady Gisela stands between Silveny and Greyfell, Silveny's mate, and shoots both alicorns with a new variant of soporidine, a dangerous sedative. She demands Tam join the Neverseen as Umber's replacement, threatening to withhold the antidote and to attack Tam's twin sister Linh. Tam agrees, reasoning that protecting Linh and the alicorns is worth the sacrifice. He hands Sophie the antidote vials before Lady Gisela knocks him unconscious and leaps away with him.

In the aftermath, Linh urges the group to focus on dismantling the Neverseen rather than risking a hasty rescue. The alicorn babies, named Luna and Wynn, successfully hatch. Sophie decides to register for matchmaking, motivated by her desire to stop letting fear control her decisions. But because her genetic parents are unknown, the system returns a devastating result: Sophie Foster is unmatchable. The story continues in Legacy.