"Praxeus" is the sixth episode of the twelfth series of the British science fiction television programme Doctor Who, first broadcast on BBC One on 2 February 2020.
The Thirteenth Doctor (Jodie Whittaker) and her companions Graham O'Brien (Bradley Walsh), Ryan Sinclair (Tosin Cole), and Yasmin Khan (Mandip Gill) search across multiple countries to investigate strange phenomena, including birds acting strangely and a British astronaut, Adam Lang.
The Doctor and her companions, joined by ex-police officer Jake, video blogger Gabriela, and medical researchers Suki and Amaru, investigate a new bacterium infecting people in Peru, Hong Kong, and Madagascar.
The Doctor determines that the bacterium is drawn to microplastics that have saturated living beings, and that the birds’ natural enzymes are trying to fight it, causing them to become violent.
When they arrive, the Doctor determines that they are at the bottom of the sea in a shell of plastic made from the Indian Ocean garbage patch.
They find Suki aboard her ship and learn that her kind came to Earth, rich in plastics, to study Praxeus and create their own antidote.
The consensus on the website reads, "A step back from the previous installment, 'Praxeus' is a mystery box that doesn't add up to much, but it's still a fun enough return to basics for Doctor Who.