A Gentleman in Moscow opens in June of 1922 as a committee of Russia’s Bolshevik government sentences Count Alexander Rostov to lifelong house arrest in the Hotel Metropol in central Moscow. As an aristocrat, Rostov might have been sentenced to death, but the committee takes into account the pro-revolutionary sentiments contained in a poem he published nine years earlier called "Where Is It Now," when the Tsar still ruled. The Count is moved into tiny quarters, on a floor once reserved for servants, but after that he is left largely alone. For the next thirty-two years, the luxury of the Metropol will remain largely preserved, as a place for the new regime’s elite to enjoy the privileges once reserved for the old elite, and also as a place where foreign journalists and dignitaries can be entertained and simultaneously spied on. 

Initially, the Count covers his living expenses using a stash of gold coins hidden in a large desk he kept with him. Within a few days of the start of his house arrest, he makes the acquaintance of Nina, a nine-year old girl with a great deal of curiosity. Nina, the daughter of a Ukrainian bureaucrat staying at the hotel, has somehow obtained a passkey that provides access to all the Metropol’s rooms and hidden spaces. Nina leads the Count on explorations of the basement, and on spying expeditions to eavesdrop on political meetings in the ballroom. It troubles the Count that whereas Nina was once interested in princesses, she is increasingly caught up in the enthusiasms of the bureaucrats and union bosses they listen in on. The hotel’s seamstress, Marina, is the Count’s sounding board and guide as he tries to understand what makes little girls tick. Unhappily, there comes a day in December when Nina has to tell the Count that she will be starting school and can no longer spend every day with him. As a farewell gift, she gives him her passkey.

The next summer, another female presence comes into the Count’s life: Anna Urbanova, a famous actress. Their first interaction is frosty, but they soon become intimate and settle into a comfortable pattern of sleeping together whenever she stays at the Metropol. Meanwhile, as the new Soviet Union is formally recognized by Western nations, the hotel starts to recover from the business slump that followed the Revolution. However, an incompetent waiter with whom the Count has a brief, seemingly inconsequential encounter, turns out to have friends in high places. This waiter, whom the Count calls the Bishop, begins to rise in rank and influence at the Metropol. One day, a complaint the Bishop lodges with a government official leads to an edict that all bottles in the wine cellar, regardless of vintage, must be sold unlabeled, at a single price. The Count, who has been following political events with concern, concludes that the way of life he knows and loves is being swept away for good. On the tenth anniversary of his beloved sister’s death, he prepares to jump off the hotel roof. Only a handyman’s coincidental, timely interruption stops him.

The day after his failed suicide attempt, the Count asks the Metropol’s maître d’ for a job as a waiter. Knowledgeable about food, and skilled in dealing with people, the Count becomes the headwaiter within four years. He, the maître d’, and the hotel chef form a Triumvirate of friends who run the Metropol’s dinner services, including the Boyarsky restaurant and special events in private rooms. The Bishop is a continual thorn in the Triumvirate’s side.

In 1930, the Count runs into Nina as she and three other members of the Young Communist League are about to travel east to help collectivize farms. One of the other members is a boy she later marries. When he is arrested in 1938 and sent to Siberia, Nina prepares to follow. She asks the Count to look after her young daughter, Sofia, for a month or two, while Nina goes to Siberia to find work and a place to live. The Count never sees Nina again. For the next sixteen years, he raises Sofia as his daughter, always with Marina advising him as a mentor and friend. The Count, for his part, becomes the informal tutor of a government official named Osip Glebnikov, who wants to learn—discreetly—about the values and culture of the West. Eventually, the Count and Osip move from books to films, and soon after are trading opinions about Humphrey Bogart movies.

By 1950, Sofia is seventeen years old and has started taking piano lessons from Viktor Skadovsky, who conducts the orchestra that plays in hotel’s lobby-floor restaurant, the Piazza. Within three years, she is studying music at the Moscow Conservatory. When she wins a competition, the Count and her hotel friends celebrate with her. As the celebration winds down, however, a visitor, Katerina Litvinova, brings the Count sad news. Katerina is the longtime lover of the Count’s friend from university days, “Mishka” Mindich. Mishka was bookish and hot-tempered, but somehow he and the Count became the best of friends. Over the years, Mishka would drop on in the Count and share the latest developments in the new, proletariat-oriented poetry movement he and others were leading. Mishka was sent to Siberia after he denounced a decision his superior made about a project Mishka had been working on. Mishka was able to visit the Count once after completing his eight-year sentence, but now he is dead. When Katerina mentions the Count’s own poetry, the Count gently corrects her: all the poems published under the Count’s name were really Mishka’s.

When Sofia is invited to participate in a Conservatory goodwill tour that will include a performance in Paris, the Count arranges, with the help of a friend at the American embassy in Paris, for Sofia to defect to the West. The Bishop, by now the manager of the entire hotel, surprises the Count at a critical moment, but the Count is able to turn the tables. He marches the Bishop down to the basement at gunpoint and locks him in a room where he will not be found for a few days. After the Count receives confirmation that Sofia has arrived safely at the embassy, he makes his own escape from the Metropol with the help of Viktor Skadovsky. The responsibility for investigating the Count’s escape lies with Osip, who chooses to let the matter drop. After days of walking, the Count returns to the site where his family estate once stood. In a tavern in a village a few miles away, he meets up with Anna Urbanova.