Cadmium II was a radioactive isotope produced as waste in the reactor aboard the JMC mining spaceship Red Dwarf. It was an explosive leak of Cadmium II that killed all but one of the crew in the pilot episode.
Cadmium II was a by-product of the propulsion system of Red Dwarf. When the inept Second Technician Arnold Rimmer of Z Shift was assigned to repair a faulty drive plate in White Corridor 159, he did a less than efficient job. Shortly afterward the Cadmium II leaked out explosively, exposing all the inhabited decks to a lethal dose of radiation. Only Dave Lister was spared, since he had been placed in a stasis booth as punishment for breaking quarantine regulations smuggling a cat on board.
This was such a massive dose that all aboard were killed almost instantly, with the radiation remaining in the background aboard ship for the next three million years. Holly managed to react in time to seal the cargo decks and send the ship out into deep space where it would not present a hazard. The radiation reduced the crew's bodies to a fine white powder, but left the inorganic matter aboard intact.
Lister's cat, Frankenstein, was safely sealed in the hold. Her kittens bred with each other and eventually evolved into Felis sapiens, a humanoid cat species. In the ensuing three million years, Holly presumably maintained the ship with the skutters and the garbage droids.
Once the background radiation had reached a safe level, Holly was able to release Lister and explain what had happened. Lister found it hard to grasp and idly started tasting the white powder. Holly explained that it was the dead crew, which caused Lister to sweep them up and bury them in space. One member of Felis sapiens, the Cat, joined him, as did the newly revived hologram of Rimmer.
Rimmer blamed Lister for the accident, arguing that if Lister hadn't kept "that stupid cat" and hadn't gone into stasis, he would have help mending the drive plate. Rimmer in great sadness stood over the remains of his body, and that of Captain Frank Hollister, which was just a small pile of white ash. ("The End")
Lister later watched a recording of the radiation leak that Rimmer had Holly make for Rimmer's own personal viewing, recording his own death. Lister saw Rimmer in the Drive Room apologising to Captain Hollister for not resealing the drive plate properly, and accepting full responsibility for any consequences. The explosive radiation leak then hit them, forcing the captain back into the porthole, and Rimmer fell to the ground and was pushed along into the adjacent Captain's Office, knocking the captain's snow globe off the table and smashing it as he died. It was from this recording that Lister discovered that Rimmer's last words were "Gazpacho Soup", which Lister determined on learning the meaning of. ("Me²")
Three million years later, Rimmer's hologram subconsciously accepted responsibility for the accident, so he was surprised when the Justice Computer found him guilty of 1,167 counts of second degree murder. Kryten was able to prove that Rimmer was too incompetent to have repaired the drive plate correctly, and that it was his superiors who were guilty for giving him the assignment. Rimmer's conviction was overturned. ("Justice")
When the ship and its crew were later recreated by the nanobots, the restored Rimmer was able to access the confidential crew files of the old Red Dwarf thanks to Lister. One of the brilliant insights he was able to bring to Captain Hollister's attention was the potential for a lethal radiation leak caused by damaging the drive plate. Although he stated that " Anybody who mis-repaired one would have to have a brain the size of a leprechaun's testicle", he still suggested new safety procedures. ("Back in the Red II")
Rimmer would later blame failures in the ship's health and safety procedures for the accident. ("Entangled")
When the Dwarfers encountered a Time Wave, they discovered a ship washed up into their time from the past, the SS Enconium. On this ship, all forms of criticism were against the law. Rimmer said that he could easily make his home there, since nobody could criticise him or even frown upon the fact that he had wiped out his own crew due to his own ineptitude. ("Timewave")
Second radiation leak
When Rimmer used a Quantum Skipper to explore The Multiverse, he found a dimension where the Cadmium II leak had not occurred, and all the original crew of Red Dwarf were still alive. Rimmer had a short conversation with an older-looking Holly (who was still the ship computer in this reality) during which Holly repeatedly told Rimmer that "everyone is alive, Arnold" (in contrast to the pilot episode, where Holly repeatedly told Lister that "everybody is dead, Dave) and Rimmer found this hard to believe.
However, Holly then announced that a radioactive leak was suddenly occurring, advising that everyone should run around screaming. Rimmer came across Captain Frank Hollister, who was trapped inside a jammed escape pod, and had a short conversation with the captain in which the captain refused to let Rimmer in. As flames began to come down the corridor, Rimmer was able to activate the Quantum Skipper and jump into another dimension before the flames reached him, although they did consume the captain inside the jammed pod. ("Skipper", Series XII)
In the first Red Dwarf novel, the accident occurs very differently. In the novel, Cadmium II is described as part of the engine coolant system. Most notably, it was not Rimmer's fault, but the cause of both a mechanical failure - which got worse due to a lack of vigilance from the officers - and a tragic coincidence. In the Drive Room, French navigation officer Henri Dubois spilled a cup of coffee over his console, just as three red warning blips appeared on it. Dubois wrongly considered them the result of his spillage. Rimmer was actually on his way to the stasis chambers at the time, which he occasionally stayed in overnight in an attempt to preserve his youth. However, Rimmer stopped by a mirror to comb his hair, and in the extra minute he was out of the stasis booth, was caught in the blast and killed. Lister was the sole survivor of a crew of 11,169. Although it had the power of a neutron bomb, turning biological matter into dust, the ship remained structurally undamaged. Holly shot the ship out of the Solar System so as to not contaminate Earth with the radiation. When Lister got out of stasis, three million years later, Rimmer was revived as a hologram as in the TV series.
In the novel, it is also stated that a tiny dose of radiation leaked into the cargo hold where Frankenstein was hiding. This minute amount was enough to accelerate the mutation of her kittens and was why Felis sapiens evolved in such a relatively short time. (Infinity Welcomes Careful Drivers)
- To date, the Cadmium II radiation leak has only been depicted twice; in "Me²", the final episode of Series I, and in "Skipper", the final episode of Series XII.
- In the original version of "Me²", the Cadmium II radiation leak is shown to be forceful and explosive, taking over the whole ship in moments, yet it is completely invisible, and without any flames. It is depicted more like a very powerful wind.
- In the remastered version of "Me²", the radiation leak occurs very similar, although in shots which were added, flames are seen pouring down the corridors and a burst of flames enter the Drive Room just before Rimmer and the captain die.
- In "Skipper", the radiation leak is also depicted as having flames pouring down the corridors, although the radiation leak appeared to progress through the ship much slower, and the crew got much more warning.
Behind the scenes
- The element Cadmium has many industrial uses involving different isotopes and alloys, some radioactive, including for batteries and colour pigments; however due to the definition of Cadmium and its isotopes, Cadmium-2 cannot exist. However, the name Cadmium II could still be used.