Lois Clary is a software engineer at General Dexterity, a San Francisco robotics company with world-changing ambitions. She codes all day and collapses at night, her human contact limited to the two brothers who run the neighborhood hole-in-the-wall from which she orders dinner every evening. Then, disaster! Visa issues. The brothers close up shop, and fast. But they have one last delivery for Lois: their culture, the sourdough starter used to bake their bread. She must keep it alive, they tell her; feed it daily, play it music, and learn to bake with it. Lois is no baker, but she could use a roommate, even if it is a needy colony of microorganisms. Soon, not only is she eating her own homemade bread, she's providing loaves daily to the General Dexterity cafeteria. The company chef urges her to take her product to the farmer's market, and a whole new world opens up.