Call of the Sea

Norah Everhart receives a package with a picture of her husband Harry, detailing coordinates to an island east of Otaheite (Tahiti). Harry had vanished after embarking on an expedition to find a cure for Norah's mysterious family illness, which is slowly killing her. Norah journeys to the island, which she had had recurring dreams of. Moving inland, she finds a camp used by the expedition, which consisted of Harry, reporter Cassandra Ward, mechanic Frank Drayton, dermatologist Ernest De Witt, stuntman Roy Granger, and their Tahitian guide Teaharoa.
The expedition had found a well used by the islanders for a ritual involving a black ichor. Impatient, Roy had used dynamite to blow open the well, accidentally killing himself and splatting De Witt's arm with the ichor. De Witt then started losing his sanity and developing skin blotches similar to Norah's. The team had attempted to replicate the ritual, but abandoned it after the ship that brought them, the Lady Shannon, had washed ashore nearby. Norah replicates the ritual, causing the well to fill with ooze with her inside. She experiences a vision in which she walks off a cliff into a river, while watched by a giant amphibious-looking creature, and finds herself transformed into a sea creature.
Norah wakes up near the crashed Lady Shannon, and finds it torn apart with claw marks, with its crew missing. Norah finds the expedition had set up another camp, and De Witt, now insane, had stabbed Frank, but was stopped and tied up, later disappearing. The team had discovered an organ carved into the rocks and used it to open a passage to a temple on the island's peak. Norah travels to the temple, where the expedition had employed loudspeakers to use the organ's music to open the temple door. This caused a rockslide, while Frank had succumbed to his stab wound. After restoring power to the loudspeakers, Norah is knocked out, and dreams of a desert surrounded by the bones of sea creatures, and of her mother's music box, which played the organ's music. Singing it, Norah opens the temple, and finds a note by Harry explaining that she is not ill, but instead changing into something new.
Norah finds gateways that allow her to transform into the sea creature she became in her vision. She arrives at a village, used by the island's inhabitants, who were 'slaves' of unknown masters. Norah finds a note by Harry explaining that the masters took their slaves to a 'sanctuary' to complete their transformation, which he intended to undergo to become like Norah, so they could be together. This led to arguments between Cassandra and Teaharoa, leading to the latter leaving the island. As Norah journeys to the sanctuary, she feels more "alive" on the island than she ever had. During a vision, a sketch of her family tree can be discovered where she is seen distantly related to an ancient god/merperson.
At the sanctuary, she finds a note from Harry in which he seems to be losing his sanity, with blood leading into the building. Norah enters the throne room, and finds a mutated corpse, with Harry's glasses beside it. Norah realizes the body is Cassandra's, who, coveting the sea creatures' immortality, had shot Harry, attempted the ritual, and died in the process. Harry understood that the ritual would not work on him, and left. He sent Norah the package, faking his death in an attempt to get her to undergo the transformation and save herself.
Depending on player choice, Norah can either complete her transformation or reject it. If she transforms, she abandons her humanity and journeys underwater for eternal life, at the cost of never seeing Harry again. If she rejects it, she lives out the rest of her remaining years with Harry. During the credits, Norah and Harry sing their favorite song, "Dear Old Pal of Mine", together. Depending on the choice, the couple will either finish the song (implying it is a memory), or be interrupted by Norah's illness. Regardless of the ending, Harry is left alone, and years later, now works as the Dean of Archaeology at Miskatonic University, contemplating whether he made the right decision in lying to Norah. If the player chose to return to Harry, he does reflect lovingly about their last few years together during which they had moved to live by the sea.