Someone is blowing up the space beacons on the space lanes and scooping up the resulting argonite fragments. The space pirates are led by Caven (Dudley Foster) and Dervish (Brian Peck), and are pursued by General Hermack (Jack May) and Major Wayne (Donald Gee) of the Earth Space Corps. The TARDIS materializes on Beacon Alpha Four. The pirates, having killed the security force there, seal the time-travellers inside the beacon and blow it up. Fortunately, their part of the beacon is ejected whole, and space jockey Milo Clancey (Gordon Gostelow) rescues them with his old rattletrap of a ship the LIZ-79, but the space pirates have the TARDIS.
The closest world is Ta, under the control of Madeleine Issigri (Lisa Daniely) of the Issigri Mining Corporation, founded by her father Dom Issigri (Esmond Knight), whom his daughter believes murdered, and by his partner, Clancey himself, who is suspected in his death. The Doctor and his companions arrive at Ta in Clancey’s ship at about the same time as the pirates (just as Zoe calculated). Caven sends some of the beacon fragments to Clancey’s home planet Lobos to throw suspicion his way. The Doctor realizes that Madeleine is in league with Caven, but she decides to turn him in to the General. However, Caven informs her that her father is alive and his prisoner, and threatens to kill him, so she changes her mind. But the Doctor et al have rescued her father. In desperation, Caven threatens to blow up the entire planet, but the Doctor foils his plot and the General takes him out.
Only Episode 2 of this six-episode bit of space-opera has survived. It was designed as a space-western, inspired by Gunsmoke and similar shows so popular in the US at the time. It features the Lawman, The Deputy, The Pioneer, The Miner, and The Businesswoman. The TARDIS crew were away much of the time, filming the War Games, and the secondary characters pretty much ran the show.