Brooks was a trooper under Lieutenant Scott who ventured into a cave system to investigate the disappearance of seven members of Professor Kyle’s archaeological expedition.
After the Fifth Doctor discovered a Cyber-bomb in a hidden compartment, he had Nyssa and Tegan escort Brooks, Scott, Kyle and what remained of the troops into the TARDIS and wait. After the bomb was disarmed, Scott requested that he and his men accompany them to find out who had planted the bomb.
The TARDIS arrived in a freighter. After the Fifth Doctor and Adric went out to investigate, Scott and his troops rested in the TARDIS. Getting impatient, Scott took Brooks, Marshall, Tegan and another trooper out of the TARDIS to investigate. They returned to the TARDIS after they lost Tegan. Scott later took Brooks and Marshall out to go to the bridge. He had Marshall stay behind and cover them and took Brooks to the bridge. The freed Captain Briggs, Berger and Adric from the Cybermen and set up a defensive barrier to keep the Cybermen back.
After the freighter went through a time warp, Scott, Briggs, Berger and Brooks decided to evacuate the ship in an escape pod, but Adric stayed behind to try to stop the freighter from crashing. Brooks and the others escaped in the pod, but Adric died when the ship crashed. (Earthshock)
Brooks, Scott, Briggs and Berger were returned to 26th century Earth by The Doctor. (Time-Flight)
BEHIND THE SCENES
Brooks was played uncredited by either Stephen Whyment or Jonathan Evans. A continuity error meant that Brooks is not seen among the troopers inside the TARDIS after they return from their first expedition: A female trooper played by Nikki Dunsford, who had been attacked and apparently killed by a Cyberman moments earlier, is shown in his place. However, since Brooks is later seen accompanying Scott and Marshall and among those evacuating the freighter, this can be taken to be his official fate.