S21E18
Cynical with redemptive arcs
Written by Peter Grimwade
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Planet of Fire Part 4

The Doctor must prevent the Master and Kamelion from exploiting a planet's volcanic gas for destructive purposes while aiding the Sarns in escaping their prison planet.

In 'Planet of Fire,' the Doctor, Peri, and their allies navigate the complexities of a planet controlled by the Trions, a civilization known for their advanced technology and peculiar social structures. The story begins with the Master, who has merged with a robotic creature named Kamelion, attempting to escape from Peri in the Master's TARDIS. Meanwhile, the Doctor and his companions, including Turlough and Amyand, discover that the planet, Sarn, is a prison world where the Trions have been exiling their undesirables. The Doctor learns that a volcanic gas, numismaton, has healing properties and could save Malkon's life. However, the Master also seeks to harness this gas to regenerate himself. As the story unfolds, Turlough, with the Doctor's guidance, works to activate a Trion communication device to call for rescue. The Doctor and Peri face numerous challenges, including navigating through volcanic landscapes, avoiding deadly creatures, and thwarting the Master's plans. The climax features a confrontation between the Doctor and the Master, culminating in the Master's demise in the planet's flames. The narrative concludes with the Doctor and Peri departing in the TARDIS, and Turlough returning to Trion, where his exile has been rescinded.


Events in This Episode

The narrative beats that drive the story

42
Act 3

The final act commences with Peri disabling the Master, reducing him to a miniature form. Simultaneously, the Doctor focuses on harnessing the numismaton gas for its healing properties, successfully curing Malkon and other Sarns, thereby challenging Timanov's rigid religious interpretations. Turlough reveals his true identity as a Trion exile and devises a plan to use his father's crashed ship's transmitter to contact Trion for rescue, offering a path to salvation for the Sarns. As the planet's seismic instability intensifies due to the Master's manipulations, the Doctor, Amyand, and Peri navigate hazardous volcanic terrain to reach the seismic control center, intent on stabilizing the planet's core. The miniaturized Master, having re-entered Kamelion's control box, fully restores Kamelion and prepares for a 'supreme renewal' through a massive numismaton surge. The Doctor confronts the Master, now fully integrated with Kamelion, in the Master's TARDIS. He formulates a strategic counter-plan: sending Amyand with a crucial temporal stabilizer for Turlough, while preparing a localized radiation burst designed to disable Kamelion's psychocircuits. The Doctor and Peri skillfully maneuver Kamelion-Master into position. Peri activates the device, causing Kamelion to collapse, and the Doctor, honoring Kamelion's plea, destroys the robot with the Tissue Compression Eliminator. With Kamelion eliminated, the Doctor races against time to control the planet's escalating energy surge. Concurrently, Turlough, having successfully contacted Trion Control and secured a rescue ship, collaborates with Amyand to evacuate the Sarns to the designated landing ground. In a desperate final bid for power, the Master emerges from his control box, attempting to regenerate within the numismaton flames. However, the Doctor's TARDIS materializes, allowing Peri to escape. The Master, caught in the uncontrolled numismaton surge, is atomized completely as the seismic control center explodes. In the aftermath, Turlough learns his exile has been rescinded. He makes the poignant decision to return to Trion, bidding farewell to the Doctor and Peri. The Doctor then invites Peri to continue traveling with him, and she eagerly accepts, solidifying her role as his new companion and marking a fresh chapter for the Doctor.