The “Great Detective” Madame Vastra (Neve McIntosh) along with her wife Jenny (Catrin Stewart) and their butler Strax (Dan Starkey), investigate the mystery of the “Crimson Horror“. Many bodies have been found completely red, with a substance on them Vastra recognizes from before the Silurians went into hibernation; it’s the venom of an ancient leech, one that petrifies the victim, but they’ve been exposed to a highly diluted version. An investigator shows Vastra optographs, one of which shocks her and Jenny; it shows the Doctor, screaming. As the mysterious Sweetville, run by Mrs. Gillyflower (Diana Rigg), proves suspicious due to how no-one who goes to live there comes out, Jenny is sent to investigate and find the Doctor. She succeeds, finding him a victim of the venom, but still alive due to his Time Lord nature; he quickly reverses the process and does the same for Clara. Clara’s presence confuses Jenny and Vastra, who saw her die in “The Snowmen“. Confronting Mrs. Gillyflower, they discover the mysterious “Mr Sweet” working with Mrs. Gillyflower is one of the ancient leeches, attached to her; she plans to use his venom to “preserve” humanity by making a rocket with it explode. However, the rocket goes off without the venom on board, thanks to Vastra and Jenny. Mrs. Gillyflower falls to her death, after being revealed to have used her own daughter to test Mr. Sweet’s venom potency, and Mr. Sweet is crushed to death by her daughter. Not bothering to answer Vastra and Jenny’s questions about Clara, the Doctor drops her off in 2013. Once Clara is back home, she finds that the Maitland children have found photos of her from “Hide” and “Cold War“, along with a picture of Victorian Clara; they threaten to tell their father unless they get a chance at time travel.