In this chapter of the four-part story, the Doctor and his companions explore a slave-labor mining society on a newly formed planet.
: The story is loosely based on the Greek legend of Jason and the Argonauts , specifically their quest for the Golden Fleece, with "Underworld" serving as a sci-fi retelling of the journey to Colchis. Critical Reception & Production [S15E18] Underworld 2
: This serial is notorious for its heavy use of Color Space Overlay (CSO) , a primitive green-screen technique, to create the cave settings. Reviewers from IMDb note that while the lasers and some CSO effects work, others look "simply awful". In this chapter of the four-part story, the