Madam Vastra and Jenny are visited by a man who tells them of his dead brother. The last image the man saw before he died was the face of the Doctor. Together with Strax they travel north to York and try to find out what happens in Sweetville and where the Doctor is. Jenny infiltrates Sweetville but before she is registered she slips away into the factory. When she is there, she finds out that it's not a factory and follows some of Mrs Gillyflower's people who carry a red fluid in a bottle. Meanwhile Madam Vastra visits the morgue and recognises the fluid that coats the dead people's bodies. It's a deadly poison from the time when the Silurians still ruled the Earth. Jenny has found the Doctor and she is able to revive him. While they search for Clara, the Doctor tells Jenny how he and his companion ended up in Mrs Gillyflower's village. They find Clara and can revive her as well when they are attacked but with the help of Madam Vastra and Strax they are able to get away. Together they soon find out that Mrs Gillyflower wants to kill humanity but when they try to stop her, she uses her daughter as a shield and escapes. Will the Doctor be able to stop the rocket and save humanity?
This was a bit of a Doctor and companion light episode but I really liked it. It's always good to see Madam Vastra, Jenny and Strax again. I especially like the funny remarks of the Sontaran and he always brings a smile onto my face. I think we will see more of the trio at the end of this series. The leech symbiont was a bit disgusting in my eyes but it made a really good story. It was a great idea that this creature could be nearly as old as Madam Vastra and that it's maybe not an alien but something that developed on Earth. I don't know why the Doctor always lands somewhere where he didn't want to go but that doesn't matter to him when he finds an adventures there. The story of Ada was a sad storyline because her mother used her to test the venom of the leech creature. It is good that she now has a perspective to got her own way. The end of this episode was really crazy when the kids confront Clara with the pictures they have found of her on the internet. I really didn't expect this and it was a nice twist at the end. We will see what happens with all of them in the next episode.