Doctor Who (1963) Season 21 Episode 15 Planet of Fire (1)

The Doctor and his companion, Peri, have just arrived on the planet Sarn, a world on the brink of destruction due to its unstable volcanoes. The two soon discover that they are not the only visitors to the planet, encountering two different factions: the devout religious group, the Trion's, and the fiery native people of Sarn, the Garm.

As they try to navigate the politics and tensions between these two groups, the Doctor discovers that the Trion's are searching for a lost spaceship containing their prince, who disappeared years ago. Along the way, they also encounter the mysterious Turlough, who seems to be hiding something.

As the Doctor and Peri assist the Trion's with their search, they begin to uncover a much larger conspiracy involving a powerful religious artifact known as the Timelash. As tensions between the Trion's and Garm escalate, the Doctor must prevent a devastating war from breaking out, all while trying to uncover the true intentions of Turlough and whoever it is pulling the strings behind the scenes.

Meanwhile, Peri finds herself caught up in her own personal drama when she comes face to face with her estranged stepfather Howard Foster, who has been following her across the galaxy after believing her to be dead.

As the episode ends with a shocking revelation about the true identity of Turlough and the mystery behind the Timelash, the Doctor and Peri are left with more questions than answers as they come ever closer to uncovering the truth behind the looming conflict on the Planet of Fire.