A wooden box in a Swedish attic carried a strict instruction: do not open until 20 years after my death. Inside was a new visual language that predates the abstraction credited to Kandinsky, Mondrian, and Malevich. This episode follows Hilma af Klint from her 1862 birth into a family of naval commanders and a childhood obsession with botany and mathematics, through her rare admission to the Royal Academy of Fine Arts in Stockholm in 1882, to a respectable career painting landscapes and botanical illustrations by day.

We explore how her sister’s death drew her into the spiritual currents of the era, the secret group of five women who held séances and practiced automatic drawing around 1896, decades before the Surrealists, and the 1906 commission from the High Masters that produced 196 paintings for a spiral temple, including the ten-foot canvases of The Ten Largest. The conversation decodes her system of color and spirals, examines Rudolf Steiner’s brutal 1908 rejection and the tantalizing question of whether he showed her work to Kandinsky, and follows the story to her death in 1944, the Moderna Museet turning down her collection as a gift in 1970, and the record-breaking 2018 Guggenheim show Paintings for the Future.

• Why the discoveries of X-rays and radio waves made spiritualism feel scientific
• Blue for the female spirit, yellow for the male, green as their union
• Attributing genius to spirits as a workaround for Victorian patriarchy
• The four-year silence after Steiner and the conscious watercolors that followed
• Her lifelong female partnerships and reading her work through a queer lens