Duchess Sonya was a White Russian emigre who settled in Istanbul, Ottoman Turkey following the Russian Revolution of 1917. Born in Belarus to an aristocratic family, she was forced to flee following the Bolsheviks' seizure of power, and she came to work as a servant at the Pera Palace Hotel by 1919. During that time, she was hired by the British Army officer George Chalmers to serve as his eyes and ears at the hotel, and, in April 1919, Chalmers sent her to secretly kill Esra Köksüz, who was posing as her already-dead twin sister—socialite Peride Efendi—in order to prevent her from foiling an assassination attempt on Mustafa Kemal Atatürk; Chalmers promised to restore Sonya's former wealth in exchange for her help. Sonya's attempt to smother Esra with a pillow failed, and she quit her job at the hotel after revealing that Lieutenant Reşat Bey was her co-conspirator in the assassination plot. During this time, she found out about the Pera Palace Hotel’s time travel capabilities. She later married the former black marketeer Halit Vatansever, with whom she had become infatuated, but Halit left her in 1920 due to his undying love for Esra, who disappeared from his life a year earlier in order to go back to her own time.
Pregnant and manic, Sonya used a time-traveling key that Halit had left behind in order to travel back to 1919. However, Sonya used the raw-power Gateway of Truth to time travel instead of the much safer method of using one of the hotel’s rooms. This amplified her mania, leading her to attack and strangle the real Peride (who barely knew Sonya or Halit at all) to death, thus setting in motion the alternate downfall of her life—as opposed to Halit leaving her because he didn’t love her (the original course of events until Esra interfered), he would then always leave her because he was in love with someone else.
After returning back to 1920, Sonya gave birth to her and Halit’s son Ahmet and later met Alexei, a Russian cashier at a hotel restaurant and mathematics professor, and married him.