Letters, loneliness and a deadly pact: With Olivier in custody, psychologists analyze her history with Fourniret to understand her role in his crimes.

A prosecutor recalls Olivier and Fourniret's sheer lack of empathy as they uncovered bodies. Later, their ownership of a château is called into question.

When the trial opens, Olivier's role as a mother spikes public fascination — and hatred. As the couple's crimes come to light, so does their sex life.

Olivier is taken out of her cell to help with a cold case in 2021, but her motives are unclear. After Fourniret's death, can she recover her humanity?