Ammonites were a kind of snail-like precursor to today's mollusks, common in the seas of the Cretaceous period, many millions of years ago. They are among the most commonly found fossils, so they must have been extremely plentiful. In this meditative and largely unstructured first feature, a young geologist is traveling by train to visit his sister in the countryside after having received a disturbing and mysterious letter from her. As he travels, he remembers his childhood fixation with rocks, nurtured by his mother, and his very strong affection for his sister.