A corpse of a clown is found in a park. Detective Shirataka Amane of Musashino Higashi Police Station begins investigating with rookie detective Uzuka Shinsaku. They find a picture of the victim holding a balloon with the number 1 and the letters TTX on social media which indicates pufferfish poisoning. Shirataka intuitively suspects that this is an incriminating statement done by a serial killer, but Chief Investigator Fukukawa Saeko denies her. Detective Kusano Seiya and other personnel of MPD First Investigative Division join the investigation, then a second murder occurs. Shirataka recalls an unsolved kidnapping and murder case from two years ago that she still regrets.
Unfortunately the movie Hakutaka Shirataka Amane no Investigation File is not yet available on HBO Max.
| Directing | Keita Motohashi | Director |
| Writing | Izumi Kawasaki | Screenplay |