Planet of Fire: Part 2

S21, E14: On the volcanic planet of Sarn, Turlough finds evidence of an old colony of Trion, his home world. With Turlough and the Doctor away exploring, Peri is left in the TARDIS with Kamelion. Her fear overwhelms Kamelion and he is forced to fully transform to reveal that he is being controlled by the Master. Peri manages to escape but will she be able to find the Doctor and Turlough again?