一个美国生物学家偷偷把珍贵的亚马逊银龙鱼带入日本,该鱼肚子里被植入了更珍贵的红龙鱼的卵巢。中途龙鱼让某华人团伙盗走,生物学家急忙聘请侦探调查,同时警方也介入了事件的追查之中。 侦探社的接线生蒲(芳本美代子饰)由于被派往追查龙鱼案件,根据种种线索显示,她来到一个工厂区内,和神秘的养鱼人夏(浅野忠信饰)相遇,对方头发凌乱,和龙鱼相伴,过着单调的生活。空荡荡的仓库里放满鱼缸,整天回荡着瓦格纳的音乐。每次有人来追杀夏,都被他轻易解决。 蒲情不自禁对他产生了情愫,但龙鱼的谜团尚未揭开。A salesman from Delta Works, a London-based computerized database, offers a one month free trial that seems uninteresting until he mentions that an operator, always selected from a group of young women in their 20's nick-named "Delta Ladies", will also be supplied in the trial period. Poo arrives at the one-man Aida Detective Agency with the Delta Mazelan 'F' Series hardware. A dragon fish has been stolen by Tetsu Tobiyama and biologist Thomas Earwing seeks its return (the Super-Red variety is worth 10 million yen). The system fails to provide info about Tetsu, but Poo worms her way into a top secret file at Delta headquarters, finding that he supplies trained assassins for use worldwide. Searching tropical fish outlets where Tobiyama shops for supplies, Poo is led to Natsuro, living alone with fish tanks, one of which contains a dragon fish. This enigmatic young man is not only mysteriously attractive to Poo, he also seems to attract the attention of hit men aimed at him.