After writing earlier in series seven, Mark Gatiss returns from his success with "Cold War" with "The Crimson Horror," a mystery set in Victorian Yorkshire. The combination of horror and science with a backdrop of polluted, grimy and industrial Northern England made for another good episode from Gatiss. 

We see the return of the strangest detective agency in Victorian London, lead by ancient lizard Madame Vastra (Neve McIntosh), her wife and ninja chambermaid Jenny (Catrin Stewart) and their pugnacious domesticated Sontaran manservant, Strax. This time, Jenny gets to take the lead with the crimesolving, infiltrating the mysterious and shadowy Sweetville factory. Mrs. Winifred Gillyflower, proprietor of the factory, has touted Sweetville as a respite to the moral decay of the late 1890s and oncoming apocalypse. 

With superstition abound, Gillyflower (Dame Diana Rigg) and her blinded daughter, Ada (Rigg's real-life daughter Rachel Stirling) bring in hapless heaven-hopefuls, only to dunk them in red goop and put them in glass containers like frozen dolls in glass cases. The red goop is an ancient toxin last seen 65 million years ago by Madame Vastra, and even Time Lords aren't immune to it. 

The Doctor and Clara, as we find out through a sequence entirely shot in grainy, "old-style" film, had arrived in Yorkshire by mistake, at first attempting to arrive in 1890s London. There, they find out that a series of red-tinted bodies had been dumped in the canal, and no one but one journalist was interested in the case. They investigate Sweetville and are captured by Gillyflower and dumped in the vats of preservative poison, which Clara undergoes successfully but the Doctor suffers from. Clara is reverted to one of Mrs. Gillyflower's mindless dolls and taken away to be arranged for the oncoming Judgment Day. The Doctor, red-tinted, unable to communicate and nearly paralyzed, is due to be dumped with the other rejects in the canal, but is saved by the blind Ada Gillyflower, who saves her "dear monster" and puts him in shackles reminiscent of Frankenstein's monster. When Jenny saves him, they set out to find Clara next.

This episode does not actually feature the Doctor (Matt Smith) very much, in comparison to other New Who episodes. During the Classic series, it was relatively common to feature Doctor-less or Doctor-lite episodes. As such, the Doctor and clever companion Clara Oswald (Jenna-Louise Coleman) are more facilitators of the unravelling of the mystery rather than at the forefront of the investigation. 

Inside Sweetville, we discover that the factory is more bells and whistles than actual manufacturing, with giant gramophones simulating industrial sounds. Instead, Mrs. Gillyflower is preserving the "Adam and Eves" of the post-apocalyptic world, and collecting the poison to kill off the rest of humanity. 

As Vastra says, the poison, which local humans call the "Crimson Horror," is actually the toxin from the "repulsive red leech". We see the leech (referred to as "Mr. Sweet," Mrs. Gillyflower's silent partner) feeding off Mrs. Gillyflower and secreting its toxin in return. 

The real highlight of the story, though, is neither the plot nor the return of the detective story, but the relationship between Ada and Mrs. Gillyflower. Rigg and Stirling portray the dysfunctional mother and daughter; Ada is devoted and dedicated to her mother and dotes on her, and when Mrs. Gillyflower rejects her as "broken" after finding out about Ada's kindness towards the "monster," she is destroyed. Mrs. Gillyflower, when confronted about her mistreatment of Ada, confesses to experimenting on her daughter and causing her blindness, and, overheard by Ada, then takes her hostage in an attempt to stop the Doctor's interference. 

For fans of Classic Who, there was also a nice shout-out to Tegan Jovanka, the "gobby Australian," companion of the Fourth and Fifth Doctors from 1981 to 1984, and a hell of a time trying to get to Heathrow, where she is supposed to work as a stewardess. In this episode, the Doctor also says, "Brave heart, Clara," a shout-out to the Doctor's oft-repeated encouragement to Tegan, "Brave heart, Tegan."

The episode ends with Clara returning to her home, where we first saw her in "The Bells of Saint John." The two children she looks after as a nanny have discovered photographs of her on the Internet, from different time periods, traveling with her "boyfriend," who must be an alien because he time travels and has a strange chin. Recall Oswin Oswald's nickname (Chin Boy) for the Doctor in "Asylum of the Daleks." I'm still waiting on my revelations about Clara, and it was a slight disappointment that this episode hinted at some sort of explanation—Jenny and Vastra were understandably perplexed that the governess they saw die in "The Snowmen" had reappeared in a different part of England with no memory of her previous life. Maybe next episode will feature some more exposition about "the impossible woman."

This episode, as reported by Blogtor Who, was the 100th New "Who" episode since its 2005 reboot. Happy birthday! Sort of! Next week, we see Neil Gaiman (who just happens to be one of my favorite authors and I'm seeing him on my birthday so this is really exciting), who last wrote the Hugo Award-winning episode, "The Doctor's Wife", write "Nightmare in Silver". This episode features the return of the Cybermen, Clara's two wards tailing along to what appears to be a theme park. After "The Doctor's Wife," mine are not the only high expectations, I would say.

What did you think of "The Crimson Horror?" Comment below!

Reach Staff Reporter Christine Bancroft here. Follow her on Twitter here.