Lieutenant Joe Sorba was a Space Corps officer on V-41. He was assigned to guard Space Beacon Alpha 4. However, the beacon was seized by Maurice Caven's band of space pirates and he was taken prisoner.
He was taken to the pirates base on Ta and put in a cell. The Second Doctor, Jamie McCrimmon and Zoe Heriot were also thrown into the cell with Sorba. Sorba suspected the Doctor to be in league with the pirates, but later decided to trust him.
Milo Clancey released them from their cell and they all made for Madeleine Issigri's office. Being chased by the pirates, the Doctor managed to block the pirates. However, Caven and two of his guards managed to get through to the office. When Caven entered the office, Sorba grabbed a gun and lunged at the pirates, but was gunned down by Caven. (TV: The Space Pirates)