Poisoned cakes, point-blank gunshots, a body dumped in a freezing river: the legend says Grigori Rasputin simply refused to die. But the cartoon villain has swallowed the real man whole, and the truth is far stranger than the myth.

This episode strips away the fiction to trace how an illiterate Siberian peasant became a holy wanderer, infiltrated the royal court, and helped precipitate the collapse of the 300-year-old Romanov dynasty. At its heart is a single genetic mutation, a mother's terror, and the medical realities that made a desperate Tsarina believe she had found a miracle worker.

• How Rasputin reinvented himself as a stranic after a spiritual crisis at the Verkhoturye monastery in 1897
• The 1912 crisis at Spala, where his order to keep doctors away may have stopped the aspirin thinning Alexei's blood
• Why h ...