Garrett Hedlund and Cillian Murphy aren't logging back in for Tron: Ares, and now we know why. Both Hedlund and Murphy starred in the last entry of the sci-fi franchise, Tron: Legacy, as Kevin Flynn's son Sam and the son of original Tron antagonist Ed Dillinger, respectively, but neither will be in Tron: Ares when it premieres on October 10.