But the terror never unfolded. On March 1, 1953, two weeks after the camps were ordered built and two weeks before the accused doctors were to go on trial, Stalin collapsed at Blizhnaya, a north Moscow dacha, after the all-night dinner with his four Politburo comrades.

After four days, Stalin died, at age 73. Death was laid to a hemorrhage on the left side of his brain.

Less than a month later, the doctors previously accused of trying to kill him were abruptly exonerated and the case against them was deemed an invention of the secret police. No Jews were deported east. By year's end, Beria faced a firing squad, and Khrushchev had tempered Soviet hostility toward the United States.

In their book, Mr. Naumov and Mr. Brent cite wildly varying accounts of Stalin's last hours as evidence that -- at the least -- Stalin's Politburo colleagues denied him medical help in the first hours of his illness, when it might have been effective.

Khrushchev and others recalled long after Stalin's death that they had dined with him until the early hours of March 1. His and most other reports state that Stalin was later found sprawled unconscious on the floor, a copy of Pravda nearby.

Yet no doctors were summoned to the dacha until the morning of March 2. Why remains a mystery: one guard later said that Beria had called shortly after Stalin was found, ordering them to say nothing about his illness. Khrushchev wrote that Stalin had been drunk at the dinner and that his dinner companions, told of his illness, presumed that he had fallen out of bed -- until it became clear things were more serious.

More telling, however, is the official medical account of Stalin's death, given to the Communist Party Central Committee in June 1953 and buried in files for almost the next 50 years until unearthed by Mr. Naumov and Mr. Brent. It maintained that Stalin had become ill in the early hours of March 2, a full day after he actually suffered a stroke.