While the Emperor leads the Dalek Fleet on a mission to conquer other planets, the Black Dalek is left in charge of Skaro. During the testing of the Daleks' Dalatomic beam missile machine, something goes wrong, creating a radioactive cloud of rust that could spell disaster for the Daleks. Tests reveal that it could rust through even their metalert casing. The Daleks begin to panic but the Black Dalek calls for order. Meanwhile Desert Station GX.YUV is hit by the cloud and collapses. In response to the incident, the Black Dalek instructs Dalek patrols on hoverbouts to destroy the remains of the station but the cloud climbs up the patrols' rays of fire and they suffer some casualties.
The Black Dalek consults the Brain Machine and it advises them to stop the rust cloud with magnets. While this is happening, a gale sends the cloud towards the City. The Daleks trap the cloud just in time and Daleks on hoverbouts separate the rust particles with oil. But as the Black Dalek leaves to begin repairs, another Daleks rusts away in front of it. The cloud has become a plague! Daleks begin killing other Daleks out of fear of catching the disease, while the Black Dalek notes that it seems strangely immune. The Emperor and the saucers return to help put an end to the crisis and an experiment reveals that the plague is not spread through contact with other victims — rather by one particular Dalek who contacts all the other Daleks. The Black Dalek!
The Black Dalek is chased away by the Emperor's Guards to get it away from the City while the Emperor consults the Brain Machine. The Emperor finds the Brain Machine already active and it confirms the Black Dalek is indeed the germ carrier. The Black Dalek reappears after having deliberately infected itself with the plague, its casing now crumbling away, stating it intends to kill itself as it killed the other Dalek plague victims. The Emperor states that the Black Dalek is too valuable to the Dalek cause and has it taken to the recasting furnace where its casing is to be repaired. As the process takes place, the Daleks begin to administer the cure and prepare to fix the damage. In all the confusion, a mysterious spacecraft lands on Skaro's surface undetected by the Daleks.
- The Black Dalek is taken to the recasting furnace.
- Excluding the spacecraft which appears at the story's end, only the Daleks are featured here as the protagonists. Showing emotions such as panic and regret, they are much more "sympathetic" characters here than they are in many other stories, including both previous and future chapters of The Dalek Chronicles.
- The notion of Black Daleks being too valuable to lose is also part of The Mutation of Time, Volume 2 of John Peel's novelisation of The Daleks' Master Plan. The destruction of the Black Dalek on Kembel is considered to be an irreparable loss by the Dalek Prime.
- Doctor Who Weekly 39-40 in black and white
- Doctor Who Classic Comics 3-4 in colour
- DWMS The Dalek Chronicles in colour
- The Emperor returns to Skaro. (COMIC: The Penta Ray Factor)
- A Monstron spacecraft lands on Skaro. (COMIC: The Menace of the Monstrons)