Palace of Treason is the second book in the Red Sparrow Trilogy by Jason Matthews.
Captain Dominika Egorova of the Russian Intelligence Service (SVR) has returned from the West to Moscow. She despises the men she serves, the oligarchs, and crooks, and thugs of Putin’s Russia. What no one knows is that Dominika is working for the CIA as Washington’s most sensitive penetration of SVR and the Kremlin.
As she expertly dodges exposure, Dominika deals with a murderously psychotic boss; survives an Iranian assassination attempt; escapes a counterintelligence ambush; rescues an arrested agent and exfiltrates him out of Russia; and has a chilling midnight conversation in her nightgown with President Putin. Complicating these risks is the fact that Dominika is in love with her CIA handler, Nate Nash, and their lust is as dangerous as committing espionage in Moscow. And when a mole in the SVR finds Dominika’s name on a restricted list of sources, it is a virtual death sentence… 
- Dominika Egorova - The story's main protagonist, she is back in her hometown Moscow and is promoted to Captain. Working as a double agent for the CIA, she starts getting the attention of the chief of Line KR, Alexei Zyuganov, who becomes her rival inside of the SVR.
- Nathaniel Nash - The supporting protagonist, he has a new asset codinamed LYRIC. Nate still acts as Dominika's handler but faces an inner conflict when attracted to new intelligence officer Hannah Archer.
- Alexei Zyuganov - Promoted to Chief of SVR's Counterintelligence, he becomes the story's main antagonist. Suspecting of Dominika and feeling envy over her prestigious career, he tries to stop her several times by hiring henchmen to beat her and sabotaging her operation.
- Simon Benford - Chief of the CIA's Counterintelligence Division, he is a supporting character who receives more attention this time. With energy and a short temper, he works hard to find the american mole who might jeopardize CIA's most important asset, Dominika Egorova.
- Marty Gable - CIA's Deputy Chief of Station in Athens and Nate's friend. He is a mentor for both Nate and Dominika. This time he is portrayed in a more humane way.
- Tom Forsyth - CIA's Chief of Station in Athens and supportive boss for Nate, he is "part of the team" and often appears in the CIA's hideouts.
- Hannah Archer - The new CIA's intelligence officer, she's assigned to support Dominika in Moscow. Bold and clever, she's ready to help Dominika and loves to work in the streets. She's aware of Dominika's relationship with Nate, but respects it even though she was involved with him before heading to Russia.
- Yevgeny Pletnev - Deputy Chief of SVR's Counterintelligence and Dominika's source from inside of the SVR, he feels intimidated by Chief Zyuganov and is convinced by Dominika to be her ally.
- Yulia Zarubina - SVR's Washington rezident, she's around 50 years old and is considered a legendary intelligence officer. She becomes the handler of american asset TRITON.
- Seb Angevine - He is the cocky and greedy Deputy director of the National Clandestine Service. After losing his awaited promotion for colleague Gloria Bevacqua he decides to be a mole for the SVR, selling information under the codiname TRITON.
- Parvis Jamshidi - Iranian scientist from a nuclear program, he becomes an asset for the SVR and is blackmailed by Dominika.
- Udranka - Dominika's friend, she's also the Sparrow who seduced Jamshidi. She often talks to Dominika as a "ghost".
- Evdokia Buchina - SVR officer and Zyuganov's new "beast", she's the one who asked to work for him. Just like her master, she enjoys executing people.