The TARDIS is not where it is supposed to be, and the Doctor is puzzled. Instead of Earth the TARDIS is instead on planet G139901KB in the Scrampus System, local name Manussa, type 314-S. Nyssa reads out more information on Manussa to the Doctor, and he becomes concerned when she says the planet was the former home world of the Sumaran Empire. Earlier the Doctor had been trying to teach Tegan and Nyssa about the TARDIS, and thinking back he realises that it was Tegan who had read out the co-ordinates to him.
In her room Tegan is asleep, but she is having a bad dream. She wakes screaming after seeing a giant snake. It is a recurring dream, and the Doctor thinks it may be more than just a dream. The Doctor asks Tegan is she knows where they are, and Tegan asks if they are on Manussa.
The Doctor is eager to retrieve Tegan's dream; it seems Tegan is still possessed by the Mara after an earlier visit to Deva Loka. He creates a device that allows Tegan to relieve her dreams and narrate them to the Doctor. The Doctor's device is also capable of preventing Tegan from dreaming, which will prevent a physical manifestation of the Mara. Tegan mentioned a snakemouth cave, and the Doctor is eager to find it. The device also prevents Tegan from hearing, meaning Nyssa must guide her.
On Manussa Lon, son of the Federator, is bored. Bored of all the ceremony that is expected of him and his family, and of the 10 yearly celebration of the destruction of the Mara 500 years earlier. The current director of Manussa, Ambril, thought the stories of the Mara were just stories, but the previous director, Dojjen, believed that one day the Mara would return.
In a market people are getting ready for the celebrations. Lon comes across a showman, Dugdale, who has a hall of mirrors, who wants him to go inside, before progressing on to a cave system, the mouth of which resembles a snake. Inside Ambril shows Lon some pictograms, and Lon asks him about the legend of the Return. Ambril tells him he believes the legend is just superstitious nonsense. Ambril then takes Lon to the chamber of the Mara. Inside the there is a wall with a snake design. At the centre is a whole where there should be the Great Crystal; it was removed when the Mara was destroyed, and is now looked after by the director, Ambril.
The Doctor, Nyssa and Tegan arrive at the cave, but Tegan is scared to go inside. Whilst Nyssa stays with Tegan the Doctor goes inside. He hears voices ahead and announces himself, where he has held by a guard accompanying Lon. Lon wants to listen to the Doctor, and he tells him about the Mara possessing Tegan and says she is just outside the cave. Lon goes with the Doctor to meet Tegna.
Outside the cave the Doctor only finds Nyssa. Tegan had been frightened by a trader selling snake toys and had run off into the town. Inside the town Tegan collapses, and is helped by a fortune teller who removes the Doctor's device from Tegan. the fortune teller admits to Tegan she is a fraud, but the Mara manages to temporarily take over Tegan, and tells the fortune teller to look in her crystal ball. Inside she sees a snake's skull before the ball shatters.
Leaving Nyssa to look for Tegan the Doctor goes to find the Ambril to talk to him about the Mara. The Doctor learns that a ceremony is due commemorating the destruction of the Mara by the Federation which is being held on the following day. Ambril is not forthcoming about the Mara legend, but after hearing about Tegan's dream his assistant, Chela, is. Chela tells the Doctor the legend says the Mara was not destroyed, merely banished, and will return again in a dream when the minds meet again in the Great Crystal. Ambril shows the Doctor a headdress that has five heads, describing it as the 'six faces of delusion'. It hadn't occurred to him, until the Doctor asks Ambril to try on the headdress, that the sixth face is that of the wearer. Ambril tells the Doctor to leave, and soon after doing so Chela catches up with him and hands him a small blue crystal - a 'little Mind's Eye' used by the Snakedancers. In the legend the Great Crystal is called the Great Mind's Eye.
In the market Tegan hides in the hall of mirrors from Nyssa. Whilst looking in the mirrors one shows her head as a snake's skull. Dugdale watches unseen Tegan starts talking to the Mara. As the Mara takes more control over Tegan a snake appears on her arm. Dugdale offers to go into business with her, but she tells him there is only one man she is after, and the orders Dugdale to fetch Lon.
The Doctor finds Nyssa, and she hand the Doctor Tegan's device and tells him she ran away from her. They head back to the cave to examine the pictograms. The Doctor takes Nyssa back to the TARDIS to test a theory about how the Great Crystal works using the little crystal he was given. As Nyssa watches the crystal lights up when the Doctor concentrates. The crystal could be able to make whatever is in the mind in reality. If the Great Crystal is able to do this and the Mara is in Tegan's mind, the Mara could become reality again.
Tegan, under the control of the Mara, leads Lon, also under the control of the Mara, and Dugdale back to the cave hoping to find the Great Crystal. She opens a hidden door in the cave, and inside Dugdale is interested in the archaeological finds and their value. Lon is unimpressed, but tells Tegan that he knows where the Great Crystal is, and how he can get hold of it. Lon returns to Ambril and offers to show him the room as a way of getting to see the Great Crystal.
The Doctor interupts a dinner to ask to warn Ambril about the Mara and the Great Crystal, and is locked up. Chela tells the Doctor is to be held until after the ceremony. Nyssa follows Chela to where the Doctor is being held, but she is caught trying to get the key from Ambril's office and locked in the same cell as the Doctor.
In the cave Lon leads Ambril into the hidden chamber full of artefacts, and Tegan, who demands to know where the Great Crystal is. Lon bribes Ambril into saying he will place the Great Crystal in its place in the cave during the ceremony by threatening to destroy the artefacts. Amrbil reluctantly agrees.
Back in his office Ambril tells Lon's mother, Tahna, of the plan to allow Lon to place the Great Crystal in its place in the cave. Chela is horrified at this idea, and helps the Doctor and Nyssa escape from the cell. They are caught during the escape, and the Doctor tries to make Ambril change his mind. The Doctor realises that Lon is under the control of the Mara. At the first opportunity, when Lon turns away, the Doctor, Nyssa and Chela make a run from Lon's palace into the market.
As the ceremony begins, and a mock snake is led through the market, the Doctor, Nyssa and Chela head into the dessert to find Dojjen. Using the small crystal the Doctor is able to link to Dojjen to let him know where they are, and Dojjen is able to find them. After allowing himself to be bitten by a snake the Doctor is able to communicate with Dojjen telepathically.
The ceremony is still going on, and the snake enters the cave where Lon is waiting. With people from the town watching Lon places the Great Crystal in its place in the cave wall. The Manussans collapse clutching their heads as the Mara fills their minds. The Mara detects that one mind does not believe; using the small crystal, liked to Dojjen's, the Doctor is able to resist the Mara, and grab the Great Crystal. This severs the connection between the Mara and the Manussans, and stops the Mara from becoming real, destroying the Mara.
- Nyssa: Sarah Sutton
- Tegan Jovanka: Janet Fielding
- Ambril: John Carson
- Tahna: Colette O'Niel
- Lon: Martin Clunes
- Dugdale: Brian Miller
- Dojjen: Preston Lockwood (1, 3-4)
- Fortune Teller: Hilary Sesta (1-2)
- Hawker: George Ballantine (1)
- Chela: Jonathan Morris (2-4)
- Puppeteer: Barry Smith (3)
- Megaphone Man: Brian Grellis (4)
- Lon's Bodyguard: Bob Mills
- Attendants: Barney Lawrence, Chris Holmes
- Snakedancer: Ray Lavender
- Demons: Derek Holt, Fred Redford
- Worthy: Jean Channon, Derek Hunt, Brian Moorhead, Sheila Vivian
|BBC 1||584. Part One||Tuesday, January 18, 1983 6:50 PM - 7:15 PM||6.7M||65%|
|BBC 1||585. Part Two||Wednesday, January 19, 1983 6:45 PM - 7:10 PM||7.7M||66%|
|BBC 1||586. Part Three||Tuesday, January 25, 1983 6:50 PM - 7:15 PM||6.6M||67%|
|BBC 1||587. Part Four||Wednesday, January 26, 1983 6:45 PM - 7:10 PM||7.4M||66%|
- Ealing Television Film Studios
- Television Centre Studio 6