（本片根據真實訪談改編而成，所有資訊皆已更名） 2015年夏天，靈異科學研究會的年輕靈媒李夢姍，接獲了友人求助。一名女童詭異跳水後，離奇昏迷，醫生也束手無策。夢珊立刻協同搭擋，前去雲林偏鄉，與當地法師著手調查、驅邪。 昏暗民房、作祟凶靈、昏迷少女，一切都跟當地溪流盛傳的「水鬼抓交替」有關。女童的父親葉牧達，是前海軍陸戰隊士官，本來不信邪，然而，隨著一連串靈異事件，女兒託夢，法師與鬼談判破裂，他不得不與夢姍等人，參與法師「牽水狀」等在地術法，結合水文技術與科技，一同從溪水追擊水鬼，試圖趕在第七天交替完成前，搶回女兒魂魄。 殊不知，開壇驅邪成功，跟著女兒回來的，卻是更恐怖的索命詛咒，那不僅牽連著當地的信仰，也攸關那藏於水底的驚悚秘密。

(The film is based on real interviews. All the characters mentioned in the movie have been renamed.) In summer 2015, Li Meng-Shan, a young female medium of the “Taiwan Society for Psychical Research” (TSFPR), got an emergent request for help from her friend. A girl had mysteriously sunk into a coma after drowning. Doctors were unsure what caused this. Together, Meng-Shan and her partner set out to the rural area of Yunlin County to investigate the bizarre event and attempt to exorcise the evil with a local Taoist priest. A dark house, a haunting ghost, and a girl in a coma – all caused by the local ghost legend: the ghosts in river would kidnap the soul of who drowned in river and sacrifice them in order to be reborn. The girl’s father Ye Mu-Da, who was a former marine sergeant, did not believe the legend at first. However, after a series of supernatural events occurred which included his daughter appearing to him in a dream and the Taoist priest failing to control the evil spirit, Mu-Da had no choice but to join the local religious ritual “Quin Shui Zhuang” with the Taoist priest and Meng-Shan. They combined hydrological techniques to chase the river ghost and to take back his daughter’s soul before the 7th day after she drowned, or else her soul would be gone forever. What they did not know was that the thing they called back was a more terrifying fatal curse. Not only was it related to the local religion, but they uncovered a horrifying underwater secret.