The Cat Is the Answer (고양이가 정답이다)

This is a linked-story novel built around Joo Gwan-sik, a high-school mathematics teacher whose life has been shaped by failure, guilt, logic, and cats. The book is not a single linear crime novel but a sequence of connected cases. Each story begins with an animal, usually a cat, but expands into human loneliness, trauma, crime, parental pressure, and the limits of pure reasoning. Gwan-sik’s mathematical mind helps him solve problems, yet the book repeatedly shows that logic alone is not enough. The missing element is empathy.

The first story, “Memories of Zero,” introduces Gwan-sik at Ain High School. He is a mathematics teacher who feeds the stray cats living around the school. He runs a small mathematics club called Zero, a name that reflects his own sense of failure. Years earlier, he had been a promising graduate student in mathematics. He wrote a short, exciting doctoral paper that seemed to open a new route into prime factorisation and even the Riemann hypothesis. At his defence, however, a young researcher named Jin Ye-ri calmly pointed out that his central set might be empty. She was right. His whole theory collapsed in public. Gwan-sik eventually completed a much duller dissertation, failed to obtain a university job, and became a high-school teacher. He still writes papers, but the old wound remains.

At school, Gwan-sik notices Nam Woo-hyun, a quiet transfer student who loves maths and feeds cats. Woo-hyun is socially awkward but brilliant. He sees errors others miss. On one test he writes “no answer” because the problem itself is invalid, and Gwan-sik realises he has found a real mathematical mind. Woo-hyun joins Zero, where students such as Sora and Min-i also gather. When Woo-hyun solves a difficult gear puzzle by turning it into a problem about rotating squares, Gwan-sik recognises that the boy’s idea may be genuinely important. He starts developing Woo-hyun’s insight into a possible new method for prime factorisation and cryptography. He gives Woo-hyun English mathematical vocabulary and encourages him, but he is also tempted by the glory of the idea. His old hunger for mathematical redemption returns.