Cadmium II was a radioactive isotope present 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. The particulars of the accident differ in the TV Series and the novels of Red Dwarf, although in the television series it was the fault of Arnold Rimmer. After the disaster, the JMC allowed the ship to drift off into Deep Space, believing everybody "had gone down with the old rust bucket." (Trojan)