SPACE PIRATES LED BY MAURICE CAVEN ARE raiding beacons made from the hugely valuable metal argonite. Blowing each beacon into eight pieces, the pirates use propulsion units to steer them away for salvage.
A passing V-ship, commanded by General Hermack, arrives too late to save Alpha 7; guards are subsequently stationed on other beacons. One such team is ambushed by Caven’s men on Alpha 4, where the Doctor, Jamie and Zoe have also landed. But not for long; the time travellers are blasted into space in a sealed section when the pirates explode the beacon, ending up separated from the TARDIS and low on oxygen.