A Middle Eastern diver's body washes ashore on Coney Island. Because of Tarik Agiza's appearance, initial suspicions are that he may have been planning a terrorist attack. As FBI agent Corbett questions, "why else would someone be diving in this muck?" Goren quickly informs Corbett that the waters around New York City do, in fact, attract recreational divers. But when the FBI analyzes Tarik's underwater camera and find photos of the Holland Tunnel, a retaining wall near the UN, and major underwater gas lines, Tarik is looking for all the world like a terrorist. In addition, erratic deposits of large amounts of cash in his bank accounts and increased travel to predominantly Muslim countries seem to support this working theory. But Goren's not buying it. His suspicions were aroused when he spotted a group of beachcombers using metal detectors when Tarik's body washed ashore. When he interviews the hobbyists, he finds that a rare Double Eagle coin was found in the belly of a bluefish the day before. Eames puts it together: Tarik was a treasure hunter, not a terrorist. In fact, the waters around Coney Island, stretching all the way to New Jersey, are referred to as 'Wreck Valley'. Many privateer ships, gun runners and slave ships went down in these waters.
Goren and Eames decide to test the value of the coin on the numismatic market. When they find that the coins have been de-valued in recent weeks, they suspect that someone has scored a few Double Eagles and has been selling them around town. They take their theory to a local coin dealer who reveals a 'hot blonde' with a pink Mercedes has sold him a few coins. When the pink Benz is tracked to Camelot Undersea Recovery Company in Brooklyn, the detectives interview the owner, Tom Stipe, who reveals that the 'hot blonde' is his wife, though the two have recently separated. He claims to know nothing of Tarik. Tom gives Goren and Eames his wife's address, but when the detectives arrive, they find her missing. Perhaps Tom had tipped her off. There is plenty of evidence to suggest she was spending large amounts of money in recent days, making her a prime suspect. In addition, Tarik's passport is found in her abandoned apartment. Upset that Tom sent them on a wild goose chase, the detectives pay him a visit and press him to reveal that he did know Tarik, and that his wife left him for the diver. He had a motive to kill Tarik, but it couldn't have been Tom: he tore his labrynthine membrane and can no longer dive. That leaves Dana, his estranged wife, as the prime murder suspect. Tom gives the detectives another bit of information: when he called Dana to tip her off that the cops were coming, she sounded 'off'. He suspects someone was in the room with her at the time, perhaps holding her against her will. Initial investigations of Dana's apartment revealed two different sets of men's underwear. Perhaps there was, as Tom suggested, a third man involved.
The detectives decide to look into who might have funded Stipe's dives. They find Simon Harper, the founder of the philanthropic Harper Heritage Foundation. Harper funded Rick's dive, but is shocked to hear that he was murdered. He relates a suspicious story to the detectives. The day before, Harper was approached by a six foot tall man who called himself "Jonesy". He claimed that Rick ran off with his money but that he would continue the treasure hunt if Harper agreed to pay him $25,000. The detectives interview a local at the marina who might have seen this man with the unforgettable Dana, and the local tells Goren and Eames that Jonesy is actually Stan 'Chilly' Chilton, whose boat was often chartered for fishing and treasure tours. Tracking the location of Chilly's boat, the detectives dispatch NYPD's Harbor Unit and board the vessel. But Chilly and Dana are long gone.
When the detectives examine Chilly's onboard laptop, they find the images of New York's key structures which were placed on Tarik's camera. Chilly was framing Tarik as a terrorist. Goren and Eames have their suspect. But just as they think they have their guy, Chilly's body turns up dead off the coast of Fire Island. They focus their attention on Dana, who they allege pulled up anchor and disappeared when Chilly went down for a dive. They believe she left him to die an agonizing death suffering from the bends because he was forced to surface quickly. She insists that she is innocent, but implicates her husband Tom, who lent her the use of one of his boats the day Chilly was killed. She takes the detectives to the location of her treasure trove and is shocked to see it ransacked and empty. Only she, Chilly and Tom knew about the location of her stash. But Tom told one other person about the location of the coins: Simon Harper, the philanthropist who funded the expedition.
Harper insists he is innocent. Why would a rich man be concerned with a few coins? But something doesn't sit right with the detectives. This is the second Civil War Era ship Harper has tried to salvage. When Goren and Eames look deeper into Harper's past, they see a family who supported the slave trade, and the bills of lading on the ships bear testimony to this ugly family secret. Goren, Eames and Ross decide to stage the salvaging of one of the damning vessels: the 'Philomela'. Harper is noticeably anxious to hear that this ship has been found and will be raised to the surface. On the ship would be proof that Harper's blood relatives defrauded the other side of the family out of moneys that were entitled to them after the war. The Harper side of the family prospered, while the Roundtree side has suffered considerably. Harper stands to lose his fortune. Under pressure from Goren and Eames, Harper reveals the truth: he killed Tarik and Chilly to protect his family fortune and to preserve the ugly secret that he has fought so hard to keep hidden.