An elderly mathematics professor, whose brilliant career came to an abrupt end after a mysterious accident, lives in seclusion at his sister-in-law's magnificent estate. Since his accident, his short-term memory lasts only eighty minutes; after that, he can remember nothing. His sister-in-law has hired eight housekeepers so far, and each has been dismissed after a short time. But with the ninth, everything changes. She quickly earns the professor's trust, and he immediately takes a liking to her ten-year-old son. With empathy and great patience, the professor introduces them to the fascinating world of mathematics. With each new equation and each new formula, bonds are formed between them that are stronger than the loss of memory—until the professor's sister-in-law abruptly puts an end to it all.