Ep 3. Orphan 55

In the third episode of Doctor Who's 12th season, titled "Orphan 55," the Doctor and her companions find themselves transported to a seemingly idyllic holiday resort on a distant planet. However, their vacation takes a dangerous turn when they discover that the planet they are on is actually Earth in the far future, and has been ravaged by catastrophic climate change. Mutated creatures and hostile survivors roam the desolate landscape, and the Doctor must fight to save both her friends and the future of Earth.

The episode follows the Doctor, Graham, Ryan, and Yaz as they arrive at the Tranquility Spa, a luxurious resort promising the ultimate relaxation experience. The group is greeted by the resort's owner, Vilma, and her team of employees, who show them to their rooms and offer them a tour of the amenities. However, things quickly start to unravel when a group of menacing humanoid creatures invade the resort, killing several guests and staff members. The Doctor realizes that the creatures are actually humans who have mutated due to exposure to a deadly chemical, and sets out to investigate the cause and find a solution.

As the Doctor and her companions explore the planet's surface, they encounter a group of survivors who have been living underground in a bunker. The group is led by a woman named Kane, who tells the Doctor that the planet is Orphan 55, a planet that was previously uninhabitable and was "adopted" by humans as a last-ditch effort to save humanity. However, due to human exploitation and lack of care for the environment, the planet's climate was irreversibly damaged and the mutated creatures began to emerge.

Through a series of perilous encounters with mutated creatures and rival factions of survivors, the Doctor discovers that the resort is built on top of a facility that was responsible for creating the deadly chemical that caused the mutations. The Doctor manages to shut down the facility and prevent the release of any more chemicals, but not before Vilma and Kane are killed in the crossfire.

The episode ends with the Doctor and her companions escaping Orphan 55 and returning to the TARDIS, reflecting on the devastating consequences of climate change and the importance of taking action to prevent further damage. The episode serves as a cautionary tale about the dangers of neglecting the environment, and highlights the impact that individual actions can have on the future of the planet.