Parts: 6
Writer: Robert Holmes
Airdates: 8 March 1969 - 12 April 1969
Production Code: YY

Doctor: second
Companions: Jamie, Zoe

Story: The Interstellar Space Corps has a problem. Deep in space, in an area once populated only by rogue mining prospectors, space beacons are being destroyed one by one. The beacons are constructed from the valuable mineral argonite, and certain groups find it easier to dismantle the beacons than to spend time and money mining it themselves. Determined to stop the argonite pirates, the Corps have begun to patrol four beacons in the Pliny Sector, in case one of them becomes the next target.

As it happens, the TARDIS materializes aboard one of these beacons, and when the guards spot the Doctor, Jamie and Zoe, they take them for pirates. The TARDIS crew suddenly find themselves being shot at for no apparent reason, and after fleeing through the beacon, they manage to shut themselves up in an empty room - just as the space pirates board the beacon to destroy it. After killing the guards and sealing the room in which the TARDIS crew are hiding, the pirates blast the beacon into eight pieces - leaving the Doctor, Jamie and Zoe trapped in an airtight coffin, separated from the TARDIS forever...

Unless stopped, the pirates will destroy all the argonite beacons in the sector, and their scheme is drawing in innocent people who they will not hesitate to kill if they must. With their careful planning, diversionary tactics and advanced technology giving them the advantage over even the Space Corps, can the pirates be ferretted out and brought to justice before they kill the TARDIS crew as well?