The Doctor and Peri should have landed on Exar 3, but the Doctor does not recognise the location. Without warning, a shot from a laser gun hit a rock, which stands directly between them. As they could not see where it came from they decided to run back to the Tardis in the hope of escaping. Suddenly they started getting an odd sensation that made them feel tired, and slowly they feel unconscious.
They woke up to find themselves in a chamber where everything was gold. The Doctor believes they were knocked out by a moisture evaporator, which was enough to knock them unconscious but not to die. A small gold alien enters and jabs the Doctor with a sharp talons indicating him towards the door. Peri try's to follow, but is told to stay where she is whilst the Doctor was taken out of the room.
The Doctor is taken to another golden room where many of these aliens stand in military way. At the very end of the room was another alien that looked different from the rest and was taller. The alien addressed the Doctor asking for his name, which the Doctor gave. The alien introduced himself as Ranon, who was the guardian of the Debans. He stated the planet was called Belstar and apologised on bringing the Doctor and Peri down here.
He said they were in need of help as they were at war with the Siros who want to control their sister planets Lostar and Kristar and all the secrets of the planets is stored in a blue rocket that is kept in the Tower of Selsor. The tower is in the Nomed Zone, which is a very deadly place. The Siroses are specially equipped to go into the zone but the Debans are not. That is why he asks the Doctor to go and retrieve the stone for them.
The Doctor agrees and along with Peri they head out to find the Nomed Zone by following the largest rock formation that was suggested by Ranon. While trying to find it, the Doctor falls down a hole and luckily survives. He tells Peri that she should come down the hole as he has found the entrance to the Nomed Zone.
They enter and find that Nomed Zone is a complex place of caves with the walls covered in golden nuggets. Peri touches one of them, which opens a trapdoor in the floor that leads them to the stone itself. Wasting no time they picked up the stone and head out the Nomed Zone and successfully give it to Ranon.
Time-Placement: Between The Two Doctors and Timelash, more precisely between Blue Box and Davros. This because the Doctor and Peri appear well acquainted with one another but they're still bickering allot amongst each other. Also, Peri wears a suit which is very similar from The Two Doctors.
Source: Cameron Stewart