In "The Death of Stalin," Beria is portrayed to have saved Molotov from an assassination ordered by Stalin. He then frees Molotov's wife and reunites the couple. Molotov resents him for this and plots to have him executed. How accurate is this? Why did Molotov resent Beria?

In the film, Molotov is portrayed as an excessively loyal party member who has been practically driven insane by his pathological need to stay true to a constantly-shifting party line, which is simply an exaggeration of his real-life personality.

Historically, Molotov's wife, Polina Molotova, had always been a rather controversial figure within the CPSU, and her downfall came due to her very close connections to the Jewish Anti-Fascist Committee in the late 1940s. Stalin became extremely suspicious of Israeli lobbying and, by extension, any Jewish connections due to American support for Israel - he viewed them as vectors to introduce corrosive American influence into the Soviet Union. The immediate series of events that prompted her arrest came about by the assassination of JAC chairman Solomon Mikhoels (on Stalin's orders) in January 1948.

Finally, in November 1948, the decision was made to dissolve the JAC as "a center of anti-Soviet propaganda...regularly providing anti-Soviet information to organs of foreign intelligence." The Politburo's resolution stipulated that "for the time being nobody is being arrested," but that didn't last long. By the end of January 1949, the remaining JAC members, including their patron, [Solomon] Lozovsky, were in prison. [Molotova] had already been expelled from the party by Politburo decision for having ties with "Jewish bourgeois nationalists", attending Mikhoels's funeral and encouraging rumors about his death, and participating in a religious ceremony in the Moscow synagogue back in 1945. Her arrest followed, on Stalin's instructions, on 21 January 1949.

...

In fact, the allegations about [Molotova] were not wild fantasies: she had been strongly pro-Israel and swept up in the Jewish cause, more so than was acceptable in a normal party context. The interrogations of her arrested relatives and colleagues in 1949 contain many plausible reports of critical comments made by her on Soviet postwar policies toward Jews, including purging them from ministries. There are reports that as early as the summer of 1946, she had told JAC people that there was no point in going to Politburo members on Jewish policy: it was Stalin's bag, and he had a "negative" attitude to Jews.

Molotova was not executed but secretly spared by Beria, as the film portrays, but was eventually sent for a stint of internal exile in Kazakhstan. The anti-Jewish atmosphere that had been generated eventually escalated into anti-Jewish persecution campaigns, most notably the infamous Doctor's Plot.

His wife's fall in turn placed Molotov under suspicion as well, and he gradually fell from grace over the course of the next four years, along with fellow member of Stalin's inner circle Anastas Mikoyan (who is also portrayed in the film).

Although Molotov and Mikoyan remained regulars in the team meetings in Stalin's office and at Politburo meetings, and Mikoyan was personally close enough to Stalin to be meeting him on holiday in the South in the summer of 1951, their political situation was precarious.

In his typical fashion when dealing with those who had fallen out of his favor, Stalin had them demoted and humiliated over time. By the time of his death, their status had so deteriorated that had Stalin lived much longer, they probably would have been arrested and executed. The film exaggerates this precariousness for dramatic effect by literally having Molotov's name on the list of those to be arrested the night of Stalin's death.

Molotov's and Mikoyan's days were probably numbered, Khrushchev concluded; "their lives were in danger." Archival documents reportedly show that the MGB had been preparing cases against them since the middle of the year. In the opinion of historians who have had access to them, a new wave of party purges and show trials was imminent, perhaps as soon as March 1953, with Molotov and Mikoyan cast in the role of Rightists. A special prison had been set up, on Stalin's orders, under direct control of the Central Committee (in effect, Malenkov) and not security services, to handle party political cases.

After Stalin's death, Molotova was rapidly rehabilitated indeed as a means by Beria to gain Molotov's support.

The day of the funeral was Molotov's sixty-third birthday, and two days later Beria gave him a birthday present. With the flair of a magician pulling a rabbit out of a hat, he presented his gift - Polina, flown in from Kazakhstan exile that day on Beria's orders...Within ten days, Polina was exonerated of any wrongdoing on Beria's initiative and her Communist Party membership restored. The Molotov's resumed their life together, as devoted, by all accounts, as they had been before Stalin had divided them.

Beria was deeply unpopular among most of the collective leadership that emerged after Stalin's death, a mixture of dislike and fear, and he became increasingly cocky over the course of 1953. A plot against him soon formed, led by Khrushchev, and eventually joined by Molotov, Kaganovich, Voroshilov, and Malenkov (the film portrays Malenkov as fence-sitting for dramatic effect, in reality when the coup occurred he was already supporting the plot). Zhukov was also indeed involved in the plot as a means to return to preeminence - he had fallen under Stalin's suspicion shortly after the end of the war due to classic paranoia about Bonapartism, and while he was far too prominent and popular to have arrested and executed, he was shoved into backwater postings.

In addition to feeling bullied by Beria, the team was frightened of him. As the man in charge of the secret police, he was presumed to have dirt on every one of them in his files. It was Khrushchev - perhaps the team member least cowed by decades of intimidation by Stalin, by virtue of his long absence and comparative independence in Ukraine - who took the initiative. It was a very tricky matter, since if Beria got wind of any planned action against him, he had the resources to reverse the plot and arrest the plotters. The first person Khrushchev spoke to about the need to remove Beria from his posts was Molotov, who understood him immediately and indicated his full encouragement with the laconic question "Just remove him?", implying that harsher measures might be appropriate. Malenkov was a more doubtful quantity, as he and Beria were old allies. It turned out, however, that Malenkov had had enough of Beria's high-handedness, as he was frustrated in his efforts to keep up collegial unity in the Presidium by Beria's refusal to go along. He joined the plot, as did Kaganovich, who brought Voroshilov on board. Khrushchev was worried about Mikoyan, who was keeping up good relations with Beria, so he didn't tell him in advance of his plans to arrest Beria, suggesting only that there might be a proposal to move him out of the MVD [Ministry of Internal Affairs] and put him in charge of oil production, to which Mikoyan agreed.

...

Beria duly showed up, still unsuspecting, at the Presidium meeting the next day, 26 June. At first, he thought it was some kind of joke when the others turned on him; indeed, his reaction suggests that not only did he think Khrushchev and Malenkov were his friends, but also that, to the degree that friendship exists in politics, they probably had been. After Beria's disgrace, when he could be blamed for everything that was wrong with the Soviet Union, it was convenient for everyone to pretend they had hated him all along, but this has to be taken with a grain of salt. The most honest of them all was the realpoltiker Molotov, who had never pretended any great love for Beria, and may well have thought in June 1953 that Beria was too dangerous to be left alive and was an enemy of socialism to boot. Yet in his 1970s conversations with Chuev, he didn't claim to have disliked him.

When Beria understood what was going on, he seemed astonished, but put up no resistance to his arrest by Marshal Zhukov (brought back from the provinces after Stalin's death to be deputy minister of defense) and the military team that Khrushchev had organized, which had been waiting outside the meeting room...Interrogated for some months (without torture, abolished from MVD practice on his instructions a few months earlier) he spoke fairly freely but confessed no significant guilt. Many other people, both associates and victims, gave testimony as well, and the scenario that emerged, as in the [Molotova] case back in 1949, came to focus on his sex life, with lurid allegations of multiple rapes, forcible abduction of young women from the street, etc. Although this subsequently entered into Soviet folklore, the story of Beria as a sexual predator seems, though not wholly unfounded, to have been wildly exaggerated. His own account under interrogation of how he conducted his relations with the women he had affairs with, including a young one picked out on the street for him by a subordinate, is basically supported by that of a singer claiming to have been his mistress...who described seduction (admittedly under intimidating circumstances) rather than rape.

In December in a closed military court...brought in its verdict: guilty of treason, anti-Soviet conspiracy, terrorism, and spying for a foreign power (working for the Muslim Musavat Party's counterintelligence in Baku during the Civil War, hence, by extension, for the British). It was clearly a verdict in the spirit of the old Stalinist trials rather than one dictated by the weight of evidence, and the death sentence was carried out immediately...

My source for all of these quoted passages is On Stalin's Team: The Years of Living Dangerously in Soviet Politics, by Sheila Fitzpatrick.