<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> 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>
what is the secret of the face of boe
what is the secret of the face of boe
You are not alone
You are not alone