将来を嘱望されていた高校球児・諸岡克彦が殺害された。容疑は、家出をしていた克彦の弟・進也にかかる。偶然、彼らの父・諸岡三郎から、家出を繰り返す問題児の進也の捜索を依頼されていた探偵事務所の蓮見加代子は、進也の容疑を晴らそうと、父親の探偵事務所長・蓮見浩一郎、愛犬マサと一緒に真相究明に乗り出す。同じ頃、製薬会社の三友製薬でも事件が起きていた。
Hasumi Kayoko (Takimoto Miori), the rookie investigator at the all-female Hasumi Detective Agency, always observes people and cases in a level-headed manner. She detests lies and secrets, and has a strong sense of justice. Her late father worked at the city news desk of a newspaper, but committed suicide 7 years ago. However, the truth lies in darkness and Kayoko's mother, Kyoko (Zaizen Naomi), the agency's director, has been secretly pursuing the facts. An incident becomes the catalyst that entwines Kayoko and the people around her, and she closes in on the truth behind her father's death.