Jack Harkness can't die , because in " The Parting of the Ways " (Doctor Who) , Rose, the Doctor and himself are in a spaceship : Satellite 5. Jack he sacrifices himself fighting the evil alien Daleks. Rose brings him back to life while suffused with the power of the time vortex, but when the power leaves her she doesn't remember doing it. However, she wasn't in control completely. She's a human, she could never control the Time Vortex. Rose brought Jack back to life, not just once, but forever. He can die… he just doesn't stay dead! Rose and the Doctor subsequently leave Jack behind on Satellite 5: Rose thinks he is dead, and the Doctor has sensed that the new immortal Jack is an abomination that the TARDIS couldn't bear to have aboard (in fact in the next series, Jack came back and the TARDIS, panicked, went almost to the end of the universe trying to shake him off).