According to Digiguide, the title of the eighth episode of Doctor Who Series 12 is The Haunting of Villa Diodati.

In the summer of 1816, the famous poet Lord Byron rented Villa Diodati on Lake Geneva. There he met and befriended the poet Percy Bysshe Shelley who was traveling with his future wife Mary Godwin (Mary Shelley). Byron’s personal physician, John Polidori, Shelley and Godwin rented a smaller house nearby. The group was also joined by Mary’s stepsister, Claire Clairmont, with whom Byron had an affair.

When constant rain kept the five indoors at the villa over three days in June, they amused themselves by reading fantastical stories, including Fantasmagoriana, which inspired them to devise their own tales of horror. It was there Mary Shelley wrote what would become Frankenstein, or The Modern Prometheus.

Doctor Who showrunner Chris Chibnall confirmed that it will feature Mary Shelley in an interview in the March 2020 issue Pilot TV magazine. When asked if he keeps a list of historical figures he’d like to feature in Doctor Who, he stated:

“We do have a list – so yeah, [inventor Nikola] Tesla was absolutely on the list, and we go meet Lord Byron and Mary Shelley later on in the series. Maxine Alderton wrote that episode, she’s a massive aficionado of the romantics, and it’s [set on] that night when Shelley was writing Frankenstein. And you’re like, these guys are going to want to go and visit them, so, yeah, you’re always looking how you can drop these figures in, in unexpected ways.”

Along with Jodie Whittaker, Bradley Walsh, Mandip Gill and Tosin Cole, The Haunting of Villa Diodati costars Lili Miller, Lewis Rainer, Jacob Collins-Levy, Maxim Baldry and Nadia Parkes.

Nadia Parkes’ CV lists her as playing Claire Cairmont so Lili Miller, pictured above with Tosin Cole and Mandip Gill, likely plays Mary Shelley.

In an interview with Radio Times, Chris Chibanall revealed that the actors were cast to closely match the age of the characters they portray so the eldest actor, Lewis Rainer likely plays Lord Byron and, in descending order of age, Jacob Collins-Levy plays Percy Bysshe Shelley with Maxim Baldry playing John Polidori.

Written by Maxine Alderton and directed by Emma Sullivan, The Haunting of Villa Diodati will air Sunday February 16, 7:10 p.m. on BBC One and at 8:00 p.m. on BBC America.