While living in England, a married couple, John and Laura Baxter, suffer the tragic loss of their young daughter, Christine, who drowns in a pond near their home. John, an art restorer, and Laura travel to Venice after the accident, as John has taken a commission to restore an old church there. While in Venice, the couple encounters two elderly sisters, one of whom claims to be psychic and can communicate with the spirit of their deceased daughter. The psychic warns them that they are in danger and should leave Venice.

Despite the eerie warning, the couple decides to stay. The city is off-season and flooded, an unsettling maze of narrow alleyways and dimly lit canals where the couple starts experiencing a series of strange occurrences and sightings, including fleeting glimpses of a childlike figure in a red raincoat similar to the one their daughter wore. The visions strain their relationship, with John skeptical of the supernatural and Laura increasingly drawn to the possibility of contact with their lost child. As they navigate their grief and the mysterious happenings in Venice, they find the lines between reality and the supernatural blurring, leading them further into the labyrinthine city.