For decades, Sarah drew hollow-eyed, gaping-mouthed faces on Bristol cards. Frontal portraits without bodies or sex, emerging from a blank, endless background — sordid smudges, often crossed out or furiously scratched, cancelled even as they surfaced on the paper.

After her death in 1994, her loved ones discovered several hundred of these enigmatic drawings. Philippe Boutibonnes — who corresponded with her for many years and owns a number of her works — retraces Sarah’s lines with his fingers and his words, recalling their final moments together.

Do these faces that stare back at us reveal some hidden truth of the philosopher? Sarah, who never depicted herself, might well appear through the layering of these hundreds of trembling figures, each emerging at the edge of extinction.