After Mulder's informant X is shot and killed by the Syndicate, he finds a valuable new ally. Mulder and Krycek travel to Tunguska, where Mulder is captured and imprisoned. Russian researchers infect Mulder with the black oil -- only to miraculously cure him. When Scully is diagnosed with inoperable brain cancer, Mulder becomes convinced that the disease is linked to her alien abduction.
