Malcolm – Assumed name of the leader of the Morthrai advance force on Earth. Third in command of a Morthrai colony ship which crashed on Earth after The Doctor collapsed a Warp Shunt created by The Master (US: The Final Problem, Part 2). When his commander was killed in the crash, Malcolm assumed his identity, usurping the rightful role of his second-in-command (US: The Armageddon Variations). The pressure of this deception causes him to become unbalanced, obsessing over the destruction of humanity and protecting his own position. Fearing exposure, he repeatedly sets up his subordinates for failure (US: Totally Real, The Defector, A Time to be Born). The Doctor exposes his true identity to the second-in-command, who executes Malcolm shortly before the Morthrai were driven from Earth (US: Nothing at the End of the Lane). In an alternate timeline, Malcolm was taken prisoner when UNIT defeated the Morthrai and was the only one of his race to survive the subsequent genocide. He was imprisoned by the United Earth regime for the next hundred years. During the centennial celebration of the Morthrai defeat, The Doctor releases Malcolm, who kills presidential advisor Steve Whitman before committing suicide (US: He Jests at Scars That Never Felt a Wound).
Do you think for once in your life you could arrive before the nick of time? -- The Doctor, Doctor Who: The Mind of Evil