Edgar Freemantle is a wealthy, 57 year old contractor who loses his right arm in an accident at a job site. Edgar begins to battle a bouts of rage during his long recovery that cause his wife to leave him. Depressed and suicidal, Edgar takes the advice of his shrink, Dr. Kamen, to "change his scenery" from Minnesota to Duma Key, a small, virtually deserted island off of Florida's gulf coast.
Edgar rents "Big Pink" an unusual house on the northern part of the small island where Edgar begins to explore his interest in art. He feels almost compelled to draw and paint, a compulsion he relates to a phantom limb sensation he has in his right arm. Edgar's youngest and beloved daughter Ilse visits Edgar shortly after he arrives to help bring him out of his shell. While exploring the island Ilse is overwhelmed by sickness as they approach the southern half of the key; a place with unusually dense growth. Ilse leaves, taking one of Edgar's paintings with her, and Edgar meets the only other residents of the island who live down the beach from him; Elizabeth Eastlake, an eccentric old woman who is a native of Duma Key, and her caretaker Wireman. Elizabeth warns him that Duma Key has never been a good place for daughters.
Wireman and Edgar become fast friends and Edgar learns of Wireman's own past in which he tried to kill himself, but survived with a bullet in his head. Like Edgar, Wireman seemed to be almost drawn to the key. As Edgar's art talent grows his paintings begin to take on a mystical quality. Edgar's is able to "see" events that are transpiring, including his ex-wife's affair with his old friend and Ilse's love life. He also draws a picture of a wraith in a red robe which he does not show anyone. The power grows as does his phantom limb sensations, and Edgar is able to effect the outside world with his painting, a talent he uses to kill a child murderer, and to remove the bullet from Wireman's head.
Wireman urges Edgar to show his paintings to a gallery in Sarasota, and the owners are highly impressed with his talent. His work catches the eye of Mary, a long time Florida art critic. Through his conversations with Mary, and his friendship with Wireman, Edgar begins to learn of the mysterious past of Elizabeth Eastlake and her five sisters who lived on Duma Key with their father and housekeeper (Nan Melda) in the 1920's. Edgar begins to become obsessed with painting pictures featuring a terrifying ship with black sails, which Edgar feels is a ship of the dead. He paints himself into a daze one evening during which he experiences a terrible specter of a pair of long dead twin girls who enter Big Pink. Understanding that the vision is real Edgar and Wireman begin to unravel the mystery of Elizabeth's past. Elizabeth asks Edgar if he has begun to paint the ship yet ?
Edgar's work is shown at a gallery sale which is a smashing success, until Elizabeth Eastlake reacts violently to the ship pictures. She dies of a stroke and Edgar becomes convinced that Elizabeth herself was an artist. With the help of Jack, a college guy Edgar hires to help him run errands, Edgar and Wireman discover a stash of Elizabeth's old pictures at her house. Edgar is able to use the psychic abilities his phantom limb affords him to "sense" the events that happened in Elizabeth's childhood. Elizabeth was a child art prodigy, who suffered a bad injury at the age of two. After the accident she began to draw amazing pictures that began to manifest themselves in the real world, including a huge frog with fangs and a living lawn jockey. Eventually, her doll begins to tell her what to draw and Elizabeth causes a small hurricane with her art that uncovers a buried treasure off the coast which her father finds. Among the treasure is a small china doll that Elizabeth insists on having.
As Edgar attempts to uncover more of the mystery of Elizabeth's past using his own talents he learns that Perse, an ancient goddess who is embodied by the china doll used Elizabeth and her talents to escape the gulf and collect souls to serve her. It is her ship that Edgar is painting, and she is the red robed wraith in Edgar's drawing. Upon learning this he descends the stairs of Big Pink to find the ship waiting for him just off shore. He is attacked by a wraith in the form of a dead man, long ago lost at sea. As the wraith attempts to drag Edgar to the ship, Wireman intervenes and is able to drive the wraith off using a silver candlestick.
Realizing that Perse has also used him, and the unique psychic ability his phantom limb has caused, Edgar tries to keep his paintings out of the hands of his friends and family who attended the galley. He is too late to save Dr. Kamen and another old friend who had visited the gallery and they are mysteriously killed. Edgar thinks he has saved Ilse by giving her burn the painting she took. However, the art critic, Mary, bought one of the ship paintings and Perse uses it to control Mary, and send her to Rhode Island where she drowns Ilse in her own bathtub. Perse does this to punish Edgar and his meddling. Grief struck, Edgar draws an Ilse in the sand outside of Big Pink.
Realizing that the key to defeating Perse lies at the old Eastlake estate on the southern part of the island, Edgar, Wireman, and Jack travel there looking for the final clues. There they experience many of the bizarre manifestations from Elizabeth's artwork, and well as, a 12 foot alligator sent to stop them, (which Wireman disposes of with a handgun). The trio find Elizabeth's old doll, and they learn that Nan Melda, the Eastlakes; housekeeper, realized Elizabeth's power and found out about Perse. Perse punished them in the 1920's by drowning Elizabeth's six year old twin sisters by driving them into the sea using the giant frog from Elizabeth's paintings. The dead twins are then used by Perse to lure the fiancee of the oldest sister (Emery) to his death in the Gulf. Nan Melda follows the oldest sister to the beach with the Elizabeth's father because the oldest sister is next. There they encounter the now dead twins, Emery, and the red robbed Perse on the deck of her ship. Nan Melda is able to hold off the wraiths using her silver braclets as Perse looks on, but the father accidently kills the oldest daughter and Nan Melda using a spear gun. The distraction works though and Elizabeth traps the china doll representing Perse in a keg full of fresh water, which Perse cannot effect because she comes from the sea (salt water).
Realizing they must find the doll, the trio find an old well containing the remains of the oldest sister and Nan Melda, as well as, the keg which has leaked dry. The trio race against the sunset, as Edgar tries to store the doll in a waterproof flashlight full of fresh water. As night falls, the twins and Emery attack Jack and Wireman who are able to hold them off using silver spear tips taken from the Eastlake home, as Edgar traps the doll with Perse speaking in his mind the whole time. Edgar succeeds, but he takes the silver braclets of Nan Melda's from the well knowing it is not over.
With Perse trapped the trio head back to the other end of the island. Edgar knows he must face his last demon alone so he walks back to Big Pink along the beach with the flashlight. He encounters Ilse who has manifested from the sand art that Edgar did earlier. Edgar sees the ship of the dead waiting, and realizes that this is the last of Perse's tricks. He reveals to the sand-Ilse that it is a different flashlight, then smashes the entity with the silver braclets.
Wireman and Edgar store the flashlight in a water tight silver container, and drop into into a very deep Minnesota fresh water lake. The book ends with Edgar sitting down to paint his final picture; a hurricane destroying Duma Key.