The mathematics professor lives in the world of numbers. After the injury, his brain only retains memories for eighty minutes; he remembers no dates, no names, no love, no friendship - nothing except factorials, prime numbers and equations. The housekeeper who takes care of him is far from mathematics, but the Professor reveals to her and her son the secret world of numbers, in which prime and understandable quantities are comparable to the scale of the Universe. Every morning they get to know each other again. Their every day is filled with everyday life, mathematics, baseball and love. The novel by Yoko Ogawa, one of the most famous writers of modern Japan, is about memory, what it means to live in the present, and about the mysterious equations that can connect people.