Shen Zhi is woken by her younger brother Shen Xingchen coughing. She returns to September 3, knowing the entire city will lose power in seventeen days. Her brother has only one and a half doses of nebulizer medicine left, and she predicts the community clinic will be out of medicine, so she stops their mother, Su He, from going there. A neighborhood announcement says water will be rationed by time slots starting on the 25th. Shen Zhi immediately hauls out basins, buckets, and tubs to store water, leaving her mother baffled. She uses an old ledger to keep track: Su He borrows 300 liters of water and 4,200 yuan in cash for medicine and food; Shen Xingchen borrows 380 yuan for medical expenses. Su He asks what she means by "the previous round," but Shen Zhi does not explain. She only says that last time, they died before her because she failed to keep accounts. Her mother hands her a black pen and tells her to change the entries to red, still not understanding. Shen Zhi tells her that the five buckets of water should be marked "borrowed," not "given," and that everyone's water use must be recorded. Her mother says their father worked himself sick keeping accounts. Shen Zhi says keeping accounts is how you know exactly what you have, so others cannot figure out your bottom line. But why, in the previous round, did her mother choose to go downstairs and trade for water rather than owe her anything?
