Short answers, pulled from the story.
Claude François de Malet was a French Republican general born in 1754 who had distinguished himself in the Revolutionary Wars. He resigned his commission in 1804 when Napoleon was crowned Emperor, and was later imprisoned after Eugène de Beauharnais, Viceroy of Italy, accused him of conspiring against the regime.
Malet used forged documents, presented to Colonel Gabriel Soulier at four in the morning on the 23rd of October 1812. The papers included not only a false report of Napoleon's death in Russia but also a fabricated promotion for Soulier, which further disoriented the ill colonel into compliance.
Colonel Doucet, the senior officer on duty at military headquarters, noticed that the forged letters dated Napoleon's death to the 7th of October, a date Doucet knew to be impossible because he had seen correspondence from Napoleon sent after that date. Doucet also recognized Malet as a sanatorium inmate and overpowered and arrested him.
Malet, along with the two generals he had freed from La Force Prison, Victor Lahorie and Maximilian-Joseph Guidal, were executed by firing squad on the 29th of October 1812. Colonel Soulier, who had been deceived by the forged papers, was executed on the 31st of October.
Malet and his co-conspirators planned to install a provisional republican government with Lazare Carnot as interim president. Despite contact with Bourbon royalist agents at the sanatorium, Malet's own goals remained republican rather than monarchist.
Napoleon did not punish the Minister of Police, the Duke of Rovigo, despite pressure from his rival Clarke. He was most troubled by the fact that none of the officials who had believed him dead had thought to immediately proclaim his infant son, the King of Rome, as Napoleon II.