Book excerpt: The 1934 murder of the charismatic politician Sergei Kirov sparked Stalin's brutal purges, and speculation about it still fascinates the Russians. Who killed Kirov, and why? In Russia, conspiracy theories about Kirov have abounded, and scholars throughout the world have tackled various pieces of the story -- but definitive evidence has eluded them. Now Amy Knight has combed the recently opened Russian archives to reconstruct this fascinating crime and analyze its effect on the Russian people. The result is at once an intriguing murder mystery and a major piece of scholarship that sheds new light on the terrors of Stalin.