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 neighbourhood 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.