This is the first book in the Embassy Row series. Sixteen-year-old Grace Blakely, an army brat with a long history of reckless injuries, arrives at the US embassy in the fictional European nation of Adria to live with her grandfather, Ambassador William Vincent, while her father's army unit deploys to the Middle East. She has not seen her grandfather in three years, since the death of her mother, Caroline, who died in a fire at her antique shop when Grace was 13. Grace insists she saw a man with a scar murder her mother that night, but security cameras showed no such person, and the death was officially ruled accidental. Ms. Chancellor, the ambassador's chief of staff, greets Grace and explains that her grandfather wants this to be a fresh start.
Ms. Chancellor places Grace in her dead mother's childhood bedroom, a pink-canopied shrine still filled with Caroline's belongings. The surroundings trigger vivid flashbacks, and Grace flees in a panic, encountering Alexei Volkov, a boy from the neighboring Russian embassy. Grace's older brother Jamie, now a West Point cadet, has charged Alexei with keeping her safe. When someone grabs Grace from behind to prevent her from falling on slippery stairs, she instinctively punches the Russian ambassador in the face during a ceremony in front of the international press, straining US-Russian relations.
That night, Noah Estaban, the son of the Israeli and Brazilian ambassadors, breaks into Grace's room and declares himself her new best friend. He leads her to a cliff-top party above the abandoned Iranian embassy, where Grace meets Rosie, a fearless 12-year-old from the German embassy; Lila, Noah's domineering twin sister; and Megan, an embassy kid whose mother works at the US embassy. When a scarf resembling the Israeli flag blows onto the roof of the Iranian embassy, Grace impulsively dives off the cliffs, swims to the building, and breaks in to retrieve it. Inside, she overhears two men speaking in Adrian, the local language. In a flash of moonlight, Grace sees one of them clearly: dark hair, strong jaw, and a scar running from eyebrow to jaw. She is certain this is the man she saw the night her mother died, the man she calls the Scarred Man.
Days later, Grace attends a ball at the palace as her grandfather's companion, a role her mother once filled. While following Alexei upstairs, she overhears the same two voices and sees the Scarred Man again. Overwhelmed, she flees the palace, reliving the night of her mother's death in vivid flashbacks. Alexei finds her collapsed on the street and carries her home.
Grace confronts her grandfather, insisting she has seen her mother's killer. He identifies the Scarred Man as Dominic Novak, the prime minister's head of security and a decorated war hero. He also reveals a file showing four other men with facial scars whom Grace previously identified as her mother's killer, all proven innocent. Shaken but unswayed, Grace enlists Noah, who becomes the first person to believe her account. Megan hacks into the palace's facial-recognition system, but the group cannot find Dominic among the recorded guests.
Grace, Noah, and Rosie begin tailing Dominic through the city but repeatedly lose him on dead-end streets. During a rainstorm, Grace discovers a hidden entrance to the ancient Roman tunnels beneath Adria. She descends and follows Dominic's torchlight, eventually overhearing him tell someone there are "many perfectly adequate ways to die" and he just has to find one (184). Terrified, she flees but exits through the wrong trapdoor into the South Korean embassy, creating another diplomatic incident.
Grace's friends follow her into the tunnels using a GPS tracker Megan planted in her sweater, and after initial resistance, she shares everything. The group breaks into Dominic's townhouse and plants hidden cameras. In his closet, Grace discovers an old leather jacket she recognizes from the night of the fire, with what appears to be dried blood on the cuff. The alliance fractures, however, when Megan discovers the embassy's file documenting Grace's previous false identifications and Noah feels betrayed that Grace withheld this history.
Grace retraces the tunnel route and emerges through a trapdoor into the US embassy itself, realizing Dominic was meeting an accomplice within the American diplomatic community. Shortly after, Dominic confronts Grace on the street, warning her not to get hurt. Shaken, Grace goes to Alexei, who leads her to the top of the city's ancient wall. She tells him everything, and Alexei believes her without reservation. A moment of romantic tension passes between them, distinct from the brotherly protectiveness Alexei has shown before.
When the G-20 summit is relocated to Adria, Grace's group realizes the world's most powerful leaders are concentrated in one location. They secure the tunnel entrance and station themselves throughout the US embassy's party. When Grace spots Dominic approaching the Russian president with something black and shiny in his hand, she leaps from a balcony onto his back. The object turns out to be a cell phone.
Ms. Chancellor then produces a newspaper photograph taken three days before Caroline's death showing Dominic without a scar, arguing that one could not have formed in that time. Devastated, Grace withdraws from her friends, begins therapy with Dr. Rainier, and takes medication. Megan later shows Grace surveillance footage of Dominic obsessively studying photographs of Caroline's shop and of Grace herself.
While searching her mother's room, Grace finds a photograph of teenage Caroline with a young, unscarred Dominic. She then discovers her mother's death certificate in Ms. Chancellor's filing cabinet, listing the cause of death as "Gunshot wound to the chest" (282), not fire. When Ms. Chancellor finds Grace with the document, Grace confronts her. Ms. Chancellor admits Grace was not supposed to see it, then gives Grace drugged water. Grace collapses.
Grace wakes bound with packing tape in a palace tower. She gnaws through the tape, kicks loose stones to create a hole in the wall, and slides down a cable to the ground. Entering the tunnels, she emerges near the G-20 closing ceremony. The Scarred Man finds her and reveals he was trying to smuggle her to safety, not kill her. He and Caroline had planned to stage her death to protect her from the prime minister, who had ordered the killing. He urges Grace to remember the night he got his scar.
Grace flees and encounters the prime minister, who seizes her and demands to know why Dominic has not killed her yet. Dominic holds the prime minister at gunpoint. As fireworks explode, Grace's repressed memory surfaces: On the night of the fire, 13-year-old Grace saw her mother lying on the floor after Dominic staged her "death." Believing Dominic was the killer, Grace picked up a gun and fired, accidentally shooting her own mother. Dominic shielded Caroline's body as the burning balcony collapsed, the debris slashing his cheek and creating the scar. Ms. Chancellor appears and shoots the prime minister, saving Grace.
In therapy, Grace speaks the words she has been unable to face: "I shot my mother" (304). Dr. Rainier explains that Grace has acute stress disorder and that her mind suppressed the memory. Grace learns that Jamie has always known and does not hate her, and that Alexei has returned to Moscow. Ms. Chancellor reveals the full story: Dominic had loved Caroline since childhood and planned to fake her death rather than carry out the prime minister's order, but Grace's intervention killed Caroline before the plan could succeed. Ms. Chancellor also reveals that Caroline had a secret professional life that made her a target and leads Grace to a hidden underground chamber filled with ancient books and weapons, telling Grace there is much more to learn.