<P> The Doctor has encountered the Face of Boe (as originally presented) three times . In "The End of the World" (2005), set five billion years in the future, the Face of Boe sponsored the safe viewing of Earth's destruction by the expansion of the Sun . The event was sabotaged, but the Face of Boe survived along with most of the guests, thanks to the Ninth Doctor's intervention . </P> <P> In "New Earth" (2006), the Face of Boe is apparently dying of old age in a New New York hospital in the year five billion and twenty - three . His nurse, one of the Sisters of Plenitude, Novice Hame, tells the Tenth Doctor that the sleeping Face sometimes sings "ancient songs", which she hears telepathically, and relates the legend that, just before dying, the Face will reveal his greatest secret to "one like himself", "a wanderer without a home", "a lonely god" (such as the Doctor). When the Doctor later asks the Face of Boe about the legend, the Face of Boe claims that the "great secret" can wait for their third and final meeting, and enigmatically teleports away to an unspecified destination . </P> <P> The Face of Boe's ostensible last appearance is in "Gridlock" (2007), in the year five billion and fifty - three, some time after a drug - induced plague has wiped out almost all life on New Earth . He had been using his life force to power the undercity of New New York, which was sealed off from the rest of the planet to save the only survivors from the now - extinct virus . The Face of Boe needed the Doctor's help to free the people from the undercity, and he uses the last of his life energy to provide a power boost to unseal the exits . As was foretold in legend, initially introduced in spin - off media, the sky (of the undercity) splits asunder just before the Face of Boe dies . In his final moments, the Face of Boe reveals his great secret to the Doctor: "You are not alone ." The Doctor tells his companion, Martha Jones, that the Face of Boe must be mistaken, but it is later revealed that there is indeed another Time Lord--the Master has survived the Time War . </P> <P> In the episode "The End of the World", the Face of Boe is described as a being of considerable influence in galactic circles and is identified as coming from the "Silver Devastation". In "Bad Wolf", set in the 2002nd Century, he is said to be "the oldest being in the Isop galaxy" (the location of the planet Vortis in "The Web Planet"). In "The Long Game", set 100 years earlier (the Face's youngest appearance), a TV network reports that he is pregnant with the "Baby Boemina", though the credibility of Satellite 5's news reporting is taken into question in the episode as well . In "New Earth", it is stated that the Face of Boe is the last of his species, the "Boekind" having died off long before . The Doctor also makes a comment that the Face of Boe is possibly over five billion years old . </P>

What is the secret of the face of boe