Severely aquaphobic Emily Black is in her final year at university studying marine biology when sudden news of her estranged grandmother's death triggers nightmares: visions of a giant eye under water, and fragments of a place she can scarcely remember from her childhood - Ngawi, a fishing village on the Wairarapa coast. Putting aside her reservations, Emily accepts the advice of friends Brian and Olivia to return to Ngawi for the funeral.
Initially Emily and her friends are entranced by Ngawi’s coastal setting and generous community. Emily falls for Greg, a charismatic local diver, and meets Jacob, an alcoholic fisherman who alludes to the area's bleak colonial history.
As the funeral day draws near Emily’s nightmares return. Brian and Olivia are disturbed by the locals' communal bathing, and notice alarming behavioural changes in each other. Jacob, blind drunk, falls into the sea. Despite her fear of water, Emily pulls him out. Afterwards, Jacob warns Emily that Ngawi is not safe for her. Greg reassures her that the town and its people are eccentric but harmless.
On the eve of the funeral Olivia goes missing. Brian finds her hours later on the pier wrapped in seaweed, babbling about a great shining eye under the water. Emily is disturbed by this revelation; she never told Olivia about the recurring image in her dreams.
Emily tries to leave Ngawi but discovers her car has been sabotaged. The next day she, Olivia and Brian are swept up by the town’s festivities. As the funeral ceremony builds to its climax, it is revealed that the event marks not just the passing of a life, but the birth of another: an ancient, malevolent force the town has kept hidden for generations; a force that is connected to Greg, Emily and the paua-shaped birthmark on her shoulder...