Rosa (Doctor Who)

In the episode, alien time traveller the Doctor (Jodie Whittaker), and her companions Graham O'Brien (Bradley Walsh), Ryan Sinclair (Tosin Cole), and Yasmin Khan (Mandip Gill), arrive in Alabama in 1955, and find themselves seeking to stop time-travelling criminal Krasko (Joshua Bowman) from preventing Rosa Parks (Vinette Robinson) influencing the American civil rights movement during the Montgomery bus boycott.

Deciding to investigate, the group learn that they have arrived the day before Rosa Parks refused to give up her seat as bus driver James F. Blake demanded on 1 December, effectively influencing the civil rights movement.

Tracing the energy, the group locate a suitcase of equipment from the future, but are unable to learn more when they are forced to flee when its owner attempts to hit them with a time displacement device.

Leaving her friends to research everything behind the critical moment on 1 December, the Doctor returns to examine the suitcase's contents, before using it to shield herself from its owner — a rehabilitated mass murderer named Krasko.

After witnessing Parks being arrested by the police for violating segregation laws, the group return to the TARDIS where the Doctor shows them the impact Rosa has had on history, leading to an asteroid being named in her honour in the future.

[1] Co-written by Blackman, she became the first writer of colour to work on the programme in its entire history (something almost accomplished by Robin Mukherjee 29 years earlier, during the run of the original series with the unmade Alixion).

The critical consensus reads "First time Doctor Who writer Malorie Blackman pens an insightful installment that returns the show to its educational roots and serves as a reminder of how powerful purposeful science fiction can be.