The character drives the story, but before she can react to her surroundings, its necessary to find out what is going on in her life.
Historicals nearly have the outline done for you. Research what was going on during the time you want to put her in. If the character lives in a world of your creation, what goes on in this world?
In HARRY POTTER there were quidditch matches all year and the Yule ball once a year. These are events utilized in the books. In Harry's world, the events centered around school. The problems were resolved before year's end when he got on the train home. The school year was her timeline.
What time of year events happen add to the story. Spring is symbolic of renewal. It's a good time to find resolution, lost loves, or inner strength.
Autumn might be a time when old habits or ideas die, or change to allow for something new.
Getting a feel for what occurs in your characters year will give you a ideas for the events in her life. Conflict is created around those events.
Kindertransport caught my attention because I never heard of it. Grafeneck Castle became one of six killing centers. These two factors made me wonder what kind of hero would defy the law and rescue a child targeted for termination.
Since Nazi's are never heroes I found the idea of a SS resistor interesting. My hero needs to defy the Reich, protect the heroine, and save the child while not blowing his cover and earning the trust of a woman with no reason to trust him.
Where to start?
The Nazi's took over Grafeneck in October of '39. She would have to get the children out before then. Prior to October, she needs to meet the hero, the villain, and the children of Grafeneck.
To start my time line I need to outline things the heroine needs to do.
My introduction needs to explain the "feel" of the people under Nazi rule and how this affects my heroine. I used the Christmas story. "Take the baby and flee; the king wants to kill him." This opening hook generates interest and foreshadows my heroine's conflict. My hero and heroine are introduced by a mutual mentor.
I also needed to introduce my villain, so I used a social event. The League of German Girls hosted several, accommodating my story nicely. It also allowed a resistance protest.
The heroine, Erika, gets a job at Grafeneck castle to care for handicapped children. Now, to give her challenges fitting the times. As a Catholic, Erika holds life sacred. She sees the attitudes people have against the attitudes. At work, a monetary reward is given for those nurses who turn in the names of "defective" babies to the state.
Any issue can be made into conflict. There are always those who agree and those who disagree. Making up her own mind sets up the conflict and goal. She has a certain length of time to reach these goals.
Decide the main story events and plot them on a timeline. Give her problems to solve and keep her reactions within her character experience, belief system and ability.
Erika's faith demands she resist Nazi policy. her problem now is about trust. There are those so indoctrinated they have no problem turning over dissidents to the state. Trusting the wrong person can mean her arrest.
Conflict will arise when each character tries to reach their goals before the story ends.
Once you have the major events down there is always time to add more and layer the story.
The outline lays the groundwork for events and what order they occur. It can change as your ideas change, but its always there for a reference point.