Edith Keeler was a social worker who ran a soup-kitchen out of the Twenty-First Street Mission, on planet Earth in 1930. Known for her compassion and forward thinking, she sought to bring peace to the entire planet. In that year, she died in an automobile accident.
After traveling back in time from the year 2267 through the sentient time portal known as the Guardian of Forever, Doctor Leonard McCoy made the acquaintance of Keeler, who took care of him while he was in a delusional state as the result of an accidental cordrazine overdose. Keeler was a strong and vocal pacifist and her ideas on space travel, new energy sources, and a peaceful society brought ridicule from those at the shelter.
Upon recovering, McCoy saved Keeler from dying in a traffic accident, unwittingly changing history. This resulted in the creation of an alternate timeline in which Keeler continued striving for her goals, and eventually founded one of the largest peace movements in the United States. Her actions finally attracted the attention of President Roosevelt, with whom she met on February 23, 1936, to confer on her plan of action for assisting the needy. By the late 1930s, the growing pacifism caused by actions Keeler set into motion would delay the United States' involvement in World War II, allowing Germany to complete its heavy water experiments and be first in the development of the atomic bomb. This, together with the V-2 rocket, enabled Germany to capture the world.
Keeler and Kirk In the future, Captain James T. Kirk and Commander Spock learned of this alteration to history from the Guardian, who told them that, due to McCoy's actions in the past, history had been altered and the Earth they knew no longer existed. Having no choice, Kirk and Spock opted to travel to the past through the Guardian's portal, hoping to undo the damage to history caused by McCoy. Arriving at a point in time before McCoy's arrival, they made the acquaintance of Keeler, with whom Kirk quickly fell in love. Upon reviewing tricorder data taken from the Guardian, Kirk and Spock learned that, in order to restore the timeline, Keeler must have been allowed to die. Reuniting with McCoy, Kirk made the difficult decision of stopping him from saving Keeler from the automobile accident, ensuring her death and thus the restoration of the timeline