"Praxeus" is the sixth episode of the twelfth series of Doctor Who, and was first broadcast on February 2, 2020, which is a somewhat ironic airdate, considering the subject matter.
An astronaut's space capsule is burning up on reentry. A former police officer is fired from his job as a security guard for tackling a shoplifter. One of a pair of women camping in Peru go missing and there are strange looking crows chasing them. A submarine has gone missing off Madagascar and The Doctor pulls a naval officer out of the ocean while companions Graham and Yaz are prowling the Hong Kong alleys, where they meet tough ex-cop Jake, who is looking for the downed astronaut. Meanwhile, companion Ryan meets Gabriele, the girl with the missing friend (girlfriend?) in Peru, searching for dead birds.
And that is the first 10 minutes of this episode. The 11th and 12th series of Doctor Who decided to give the new Doctor three companions to travel with, which seemed like a good idea, but hadn't been giving them much character development. This episode solves the problem by breaking them into teams and, in turn, giving them their own "companions", the shows guest stars, as they run around the globe trying to figure out the mystery of a disease that causes people's skins to calcify into scales and then explode, which I found grotesquely satisfying.
The scientific explanation for all of this is given rather hastily: plastic eating bacteria have colonized earth because we have so much waste plastic, and then it uses ingested microplastics as a vector to infect more people for---reasons? And it is up to The Doctor to engineer a bacteriophage virus to combat it, which of course she does at the last minute, even though at the last minute it turns out the situation isn't exactly what it seems. But luckily, due to Graham helping ex-husbands Adam (the astronaut) and Jake (the cop) reconcile, the world is saved from disaster.
I really liked the first 15 minutes of this episode, as the globe-spanning action was the type of dizzying, if non-sensical fun, I had come to expect from Doctor Who. Towards the middle, it kind of bogged down in a combination of sentimentality (making a separated couple two masculine gay men doesn't mean that plots featuring them will not be sappy) and hand wave science. The ending was truer to form, and overall, I left this episode feeling satisfied, but not amazed.
As mentioned, this was released in February 2020, when Covid-19 was still just a news story outside of China. Since it featured a potential globe-spanning pandemic, its timing was interesting. Documents of how people portrayed the idea of pandemics before Covid-19 will probably be of great interest in the coming years, as we compare the crisis that disease was portrayed as to people's sometimes nonchalant response to the real pandemic.