After being murdered, ordinary woman Zhang He is reincarnated as a cockroach named Zhang He. The only way to turn back into a human is to bring her killer to justice. Relying on her cockroach colony, Grandma Mouse, and Spider Bro, she forms a miniature detective squad and takes online cases in exchange for biscuits. They gather evidence of the killer's psychological abuse, home invasions, and threats, one case after another. In the end, the killer exposes his own murder crime, and the villain finally faces justice. Zhang He continues running her insect detective agency, waiting for her chance to come back to life.