Henry McMullan was a member of Lord Jack Corrigan's twenty-four man party that stole a Drelleran ship, the Aeolus, and discovered their secret to long life. They subjugated the Drellerans, who, after being servile for a time, infected the humans with a virus that prompted them to return to Earth with a desire to wipe out their species.
McMullan was sent ahead of the Aeolus to board Space Dock Nerva. He used touch to infect Laura Craske, causing the two to physically bond together. The Drellerans injected the Fourth Doctor, Leela and Alison Foster with an anti-virus. When they came into contact with the infected, the virus was destroyed. McMullan, Corrigan and the other original party members decayed to their actual age and died. (AUDIO: Destination: Nerva)