The young son of Mai Takano, Sho is kidnapped and the only clue to his disappearance is a note starting with the words “This is a quiz…." Chief investigator Kaoru Kiriko of the Special Investigation Team goes down a trail of the kidnapper’s increasingly perplexing riddles mocking the efforts of the police. Street-smart Kaoru may be the kidnapper's intellectual match, but as she gets closer to her mark, she finds herself becoming the hunted rather than the hunter.