: The Doctor and the Paternoster Gang thwart the launch. In the aftermath, Mrs. Gillyflower's abused daughter, Ada, destroys Mr. Sweet after her mother falls to her death. Key Themes & Creative Highlights

: Mrs. Gillyflower’s "silent partner," Mr. Sweet, is revealed to be a prehistoric red leech from the Silurian era attached to her chest in a symbiotic relationship.

: Mrs. Gillyflower (played by Dame Diana Rigg) plans to launch a rocket to spread a prehistoric red leech venom across the globe, wiping out humanity to "restart" the world with her preserved chosen few.

Set in 1893 Yorkshire, the story centers on the mysterious "Crimson Horror," a condition that leaves victims dead with bright red skin.