Michael Strogoff, a 30-year-old native of Omsk, is a courier for Tsar Alexander II of Russia. The Tartar Khan (prince), Feofar Khan, incites a rebellion and separates the Russian Far East from the mainland, severing telegraph lines. Rebels encircle Irkutsk, where the local governor, a brother of the Tsar, is making a last stand. Strogoff is sent to Irkutsk to warn the governor about the traitor Ivan Ogareff, a former colonel, who was once demoted and exiled and now seeks revenge against the imperial family. He intends to destroy Irkutsk by setting fire to the huge oil storage tanks on the banks of the Angara River.
On his way to Irkutsk, Strogoff meets Nadia Fedor, daughter of an exiled political prisoner, Basil Fedor, who has been granted permission to join her father at his exile in Irkutsk, the English war correspondent Harry Blount of the Daily Telegraph and Alcide Jolivet, a Frenchman reporting for his 'cousin Madeleine'. Blount and Jolivet tend to follow the same route as Michael, separating and meeting again all the way through Siberia. He is supposed to travel under a false identity, posing as the pacific merchant Nicolas Korpanoff but he is discovered by the Tartars when he meets his mother in their home city of Omsk.
Michael, his mother and Nadia are eventually taken prisoner by the Tartar forces. Ivan Ogareff alleges that Michael is a spy. After opening the Koran at random, Feofar decides that Michael will be blinded as punishment in the Tartar fashion, with a hot blade. For several chapters the reader is led to believe that Michael was indeed blinded, but it transpires in fact that he was saved from this fate (his tears at his mother evaporated and saved his corneas) and was only pretending.
Eventually, Michael and Nadia escape, and travel to Irkutsk with a friendly peasant. They are delayed by fire and the frozen river. However, they eventually reach Irkutsk, and warn the Tsar's brother in time of Ivan Ogareff. Nadia's father, who has been appointed commander of a suicide battalion, and later pardoned, joins them and Michael and Nadia are married.

Question: What was Strogoff sent to warn the governor about?
Answer: Ivan Ogareff's revenge plan against the imperial family.
Alternative answer: The traitor Ivan ogareff