The story begins in 1903, when the Polish-born Marie (played by Polish actor Karolina Gruszka) and her French husband, Pierre (Charles Berling), have just received the Nobel Prize in Physics for their research in radiation. They continued work in their personal lab, actually a refitted garden shed, working to isolate the elements polonium and radium, which they had discovered years earlier.
Director Marie Noelle (co-writing with Andrea Stoll) depict the Curies as a happy couple, caring for their two daughters and working feverishly in their lab. That ends in 1906, when a horse-drawn cart runs over and kills Pierre as he crosses a street.