Chekhov's Journey

In 1890 the Russian author Chekhov undertook an historic journey across Siberia to the convict island of Sakhalin. A hundred years later, in an isolated artist's retreat, a Soviet film unit prepares to commemorate his journey by using a technique that will cause their chosen actor to not only play the role of the playwright, but to believe that he is Chekhov.

But the situations Mikhail acts out diverge wildly from known biographical facts when Chekhov hears of an explosion in the Tunguska region of Siberia. Yet the real Tunguska explosion occurred in 1908 - so how could Chekhov have possible heard of it in 1890?