It broke the unwritten rules of The Companion Chronicles by featuring Nyssa relating an adventure with the Fifth Doctor. Typically, the range dealt with incarnations of the Doctor whose actors were not able or willing to participate in monthly Doctor Who releases. Nyssa was the Fifth Doctor's most constant audio companion, so her inclusion in this range was unusual at the time. However, Turlough, Peri Brown, Evelyn Smythe, Ace, Bernice Summerfield and Charlotte Pollard each later appeared in at least one Companion Chronicle.
Separated from the Doctor after an accident, Adric, Tegan and Nyssa find themselves at the mercy of the Traders' curiosity. But the Traders have salvaged a cabinet from the battle that could be very dangerous indeed.
To find the Doctor, the TARDIS crew will have to enter a violent inter-planetary war. Where someone will die, and it will change everything.
Having detected a dimensional anomaly, the Doctor materialises the TARDIS on a rapidly deteriorating ship. Although there is seemingly no atmosphere, he and his companions are nevertheless able to breathe. Shortly after their arrival, Nyssa sees a figure moving in her peripheral vision, which she soon discovers is a Dar Trader. She describes them as producing a smell similar to ammonia. The Doctor has never previously heard of the Dar Traders. One of them claims that the four of them have "shifting death signatures. The Dar Traders, who not only trade but consume the dead, have no jurisdiction over the living.
After the structure of the ship further destabilises, the corridor in which the Doctor, his companions and the Dar Traders are standing splits in two. While Adric, Nyssa, Tegan and one of the Dar Traders remain in the half of the corridor which is still connected to the main body of the ship, the Doctor ends up on the other half, although he has access to the TARDIS. The second Dar Trader is blown out into space. Given the unstable nature of the ship, the surviving Dar Trader suggests that he, Adric, Nyssa and Tegan retreat to his vessel.
The walls of the Dar Traders' vessel are adorned with the carcasses which they have previously collected and salvaged. They are preserved using formaldehyde. Tegan describes the remains as "ghoulish." The Dar Trader tells them that they collect the carcasses in order to discover the experiences of the deceased at the moment of death. The Dar Trader's scanners detect that the TARDIS has materialised on the surface of the planet below, leading Adric to suggest that it is once again malfunctioning. The vessel features dozens of Dar Traders in stasis. They are attempting to discover what, if anything, exists in the threshold between life and death.
While in the Dar Traders' catalogue device, Nyssa experiences a vision of herself being held by Tegan in a field of leaves. The Dar Trader interrupts the cataloguing process and states that, as a Trakenite, death is attracted to Nyssa but she can master and calcify it. He proposes a trade. Nyssa agrees on the condition that he spare Adric and Tegan from the cataloguing process and that they retrieve the Doctor and the TARDIS from the planet. The Dar Trader tell Adric, Nyssa and Tegan that they trade in death as they sought to experience it without actually dying.
The pod which the Dar Traders retrieved from the planet is constructed from dwarf star alloy, an extremely dense metal often used to aid in the travel between dimensions. Adric, Nyssa and Tegan determine that this was the source of the dimensional anomaly.
In a secret compartment of the pod, Adric, Nyssa and Tegan discover a middle-aged man dressed in a black suit with a red shirt. Although the Dar Trader believes that he is dead, the man opens his green eyes, pulls out a dagger and stabs Adric in the chest. However, he did not die as he is an Alzarian, meaning that his heart was on the right side of his chest rather than the left. Having been restrained by the Dar Trader, the man tells Nyssa that he is an assassin for hire named Damasin Hyde.
On the surface of the planet, Damasin discovers that his ship has been raided and all of his equipment has been stolen. His intended target is the Doctor. He has gained possession of his glasses. The Dar Trader claims that he can locate the Doctor by tracking his death signature.
Damasin, who claims that killing people is something that he is "exceptionally good at", tells Nyssa that he cannot die as his cabinet is able to keep him in a perpetual state between life and death, meaning that he is the perfect assassin as he is incapable of being killed.
After being stabbed by one of the soldiers who survived the battle, Nyssa is dead for three minutes but she is brought back by the Dar Trader, who conducts a trade with her. She awakens to find herself being cradled by Tegan in a field of leaves, which is consistent with her earlier premonition while in the catalogue device.
During Nyssa's convalescence, the Dar Trader and Damasin locate the Doctor in a nearby town. They find him on his knees outside the TARDIS being threatened by a several ragged soldiers, who seek to gain possession of the TARDIS key. Damasin kills them.
The TARDIS was unable to materialise on the disintegrating ship as it was dragged to the surface of the planet by Damasin's vessel. He tells the Doctor that he requires a Time Lord in order to power his cabinet, given its enormous power requirements. Damasin shoots the Doctor but he survives. He determines that the cabinet is the source of the dimensional anomaly and that if Damasin were to activate the cabinet using the Doctor's energy, the dwarf star alloy would amplify the effect and create a hole in the universe, destroying the entire planet.
By bonding herself with the Doctor's energy in the cabinet, Nyssa enters the threshold and turns Damasin to stone.
- Nyssa states that she was familiar with the theory of dimensional transcendentalism before travelling with the Doctor.
- The pod which the Dar Traders retrieved from the planet is constructed from dwarf star alloy.
- This is the first Companion Chronicle to be read by a companion of a Doctor other than the first four incarnations, though Nyssa was briefly a companion of the Fourth Doctor in the television story Logopolis.
- This is the first Big Finish audio play to feature the Fifth Doctor, Nyssa, Tegan and Adric. This had previously been impossible as at that time neither Matthew Waterhouse nor Janet Fielding were willing to appear in the range, with the exception of what was originally intended to be Fielding's return in The Gathering in September 2006. However, Fielding would later reprise her role as Tegan on an ongoing basis in the Main Range, beginning with Cobwebs in July 2010. Waterhouse would later reprise his role as Adric, beginning in 2014 in Psychodrome and Iterations of I, and later in the Main Range, beginning with The Star Men.
- This audio drama was recorded on 1 August 2008 at The Moat Studios.
- It was first released on 3 December 2008.
- This story is set between Black Orchid and Earthshock.
- This story was told from Nyssa's perspective.
- Nyssa mentions her suffering from Lazar's disease and her departure from the TARDIS. (TV: Terminus)
- Nyssa refers to the destruction of Traken by the Master in 1981. (TV: Logopolis)
- The Dar Trader states that death follows Adric closely. (TV: Earthshock)
- Adric reminds Nyssa that Alzarians are able to heal faster than other species. (TV: The Visitation)
- Nyssa mentions the Master stealing her father Tremas' body. (TV: The Keeper of Traken)
- During his seventh incarnation, the Doctor would encounter the Dar Traders once again on Antikon. (AUDIO: The Death Collectors)