佐木 (岩﨑大昇) に誘われ、民宿を訪れた一 (道枝駿佑) と美雪 (上白石萌歌) は、居合わせた合宿中の美大生達と肝試しをすることに。舞台となった病院のトイレには、患者だった『花子』の霊がいるらしい。クジの順番通り花子さんの個室を訪れる中、最後に向かった伊能 (中川大輔) の姿が消える。床には花子さんの墓まで続く血の跡があったが、インクだと判明し、伊能によるイタズラだと思われた。しかし、翌日死体が発見されて…。
佐木（岩崎大昇飾）帶一（道枝駿佑飾）與美雪（上白石萌歌飾）來到他親戚所經營的民宿。正好有4位藝術大學的學生在這間民宿集訓，他們邀一等人參加試膽大會。佐木覺得這是能增進一與美雪感情的絕佳機會便煽動一參加。試膽大會的舞台是已於30年前關閉的醫院。有一個鬼故事內容為廁所有一位曾是住院病患，名叫『花子』的少女鬼魂，向她搭話的人都會被殺死。試膽大會的規則是大家每隔10分鐘各自前往女廁中花子所在的裡面那間廁所，說完「花子，一起玩吧」後，將罐中的乒乓球拿回來。試膽大會照著抽籤的順序進行，最後出發的伊能（中川大輔飾）卻沒有回來。伊能總以一副盛氣凌人的態度把鳴澤（小野寺晃良飾）耍得團團轉，他還為了前女友真紀（田邊桃子飾）的事與獅子島（篠原悠伸飾）形成三角關係。廁所的地板有一道延續至花子之墓的血跡，結果一行人發現那只是墨水。大家都覺得那是喜歡嚇人的伊能所做的惡作劇。但他們卻在隔天發現伊能的屍體！當眾人懷疑是隨機殺人的歹徒犯下的罪行，一則認為隱藏在花子亡靈背後的狡猾殺人犯就在這群人之中。
Saki takes Kindaichi and Miyuki to an inn owned by his relatives. At the inn, they meet four art college students, who invite Kindaichi and the others to take part in a dare. Saki, who is rooting for Kindaichi and Miyuki to get together, convinces them to participate. The setting for the dare is a dilapidated hospital that was closed down thirty years ago. At the hospital, the art students tell them the tale of Hanako, the ghost of a patient that still dwells in one of the toilet stalls. Anyone who calls out to her is said to be killed. The dare is for each participant to go inside Hanako's stall at the very end of the bathroom, say "Hanako, let's play," then bring back a ping-pong ball from a can to prove that they did the dare. They each get ten minutes to do so. They take turns according to the lot they drew, and one by one, each participant returns. But Ino, who was the last person to go, leaves for his turn and never comes back.
