The film opens aboard an Italian ocean liner, Antonia Graza, in May 1962. Dozens of wealthy passengers enjoy dancing in the ship's luxurious ballroom while a beautiful Italian woman sings "Senza Fine." Away from the party in an outer room, a gloved hand pulls a switch that unravels a thin wire cord from a hidden spool.Suddenly, the spool snaps and the wire slices across the deck (dance floor) like a blade, bisecting the dancers. A number of them remain alive for several seconds before grasping that they have been cut in half. Only little Katie, dancing with a ship's officer (the Captain), is spared, thanks to her small stature and to the captain leaning down on her when he saw the wire snap. Seeing the fate of the other dancers, she looks up at the officer's face. He looks back at her sorrowfully, as his face splits open at mouth level and the top of his head falls off. Katie then screams, the view from the outside of the ship zooms down underwater, and the film cuts to the present day.A salvage crew has retrieved a sinking ship in the open ocean. They bring the ship into port and receive its salvage value from the authorities. While celebrating their success at a bar, Jack Ferriman, a Canadian Air Force pilot, approaches them and says he has spotted a mysterious vessel running adrift in the Bering Sea. Because the ship is in international waters, it can be claimed by whomever is able to bring it to a port. The crew soon set out on the Arctic Warrior, a small tugboat. While exploring the abandoned ship, they discover that it is the Antonia Graza, an Italian luxury liner that disappeared in May 1962 and was believed to be lost at sea. The ocean liner's disappearance was well known at the time.When they board the ship and prepare to tow it to shore, strange things begin to happen. Maureen Epps claims to have seen a little girl on the stairwell while trying to save a crewmate from falling through the floor. Greer claims to have heard the singing of an unseen songstress in various places on the ship. Epps and Ferriman discover the corpses of another team of salvagers in the ship's laundry room. The crew decide to leave the ship but take the large quantity of gold that they find on board. Their tugboat explodes from a tank of propane that mysteriously is opened as the engine is started, killing Santos, who was trying to fix the boat, and leaving them stranded on the ghost ship in the Bering Sea.As they decide to attempt to fix the Antonia Graza and sail it back to land, more and more crew members are killed, as they discover more dark secrets about the ship, including bullet holes in the pool, and a skeleton hanging by a noose in a wardrobe. Maureen Epps meets a young girl named Katie who was seen at the beginning of the movie dancing with the Captain who reveals a dark secret: the crew turned on the passengers and each other in an attempt to get the gold that the ship carried. It is revealed that the skeleton hanging from the noose is Katie, who was on her way to New York to be with her parents.Katie takes Maureen momentarily back to the past, where Epps finally sees what had happened. While the numerous dancers were sliced by the wire, the chefs in the kitchen were murdered and the crew began pouring rodent poison into the evening's food. The food was served, and it is obvious that people begin to succumb to the poison as their mouths dripped with foam. The crew begins taking the lives of the rest of the passengers, including Katie, as it dawns that it was Katie's skeleton Epps found earlier. The murderous crew also line some passengers by the pool and shoot them (accounting for the shell casings and bullet holes). As the crew begins to take the gold, one crew member (an officer) walks out of the small compartment where the valuables are stored. He takes a look at Francesca, the ship's sultry ballroom singer, who is also standing there dressed in a shimmering red satin strapless ballgown, turns around, and viciously murders his fellow crewmates out of greed with a submachine gun. Francesca then shoots him in the head with a pistol. At last, a man walks up to Francesca and they embrace. As he walks away, the singer looks up and sees a large hook swing into her face, killing her. The man burns a mark into her hand, and it is revealed that he, the mastermind of the attack, was Jack Ferriman, an evil spirit.After this enlightenment, Epps decides to blow up the ship, but is confronted by Ferriman, who has killed the last remaining of Epps' crew. He states the obvious - by using the gold as bait, he has taken multitudes of souls to his masters; he has been doing this for a long time, and considers himself a "salvager" of souls. He guided the salvagers there merely to effect repairs. They fight for a short amount of time before Epps manages to blow up the ship, "killing" Ferriman. She is left in the debris as the souls trapped on the ship ascend to heaven; Katie stops to thank her.Epps is discovered by a large cruise ship and taken back to land. The last scene shows Epps in the back of an ambulance at the docks. She looks out the back of the vehicle from her stretcher and sees the battered crates of gold being loaded onto the cruise ship by the her former crewmen, followed moments later by Ferriman. He glares at her, and carries on, her screams cut short by the ambulance doors closing and the fade to the end credits.
Output: Question: What do they discover?, Answer: Which they?