The discovery of a shipwreck off the coast of South Africa has the academic career of failing lecturer Dr. Billy Malgas back on track. However, he and his assistant decide to keep it a secret until the ship has been salvaged. To aid them with the publicity, Malgas contacts an old acquaintance to film the salvage for a documentary - none other than investigative journalist Sam Cleave.
Sam enlists the help of his usual partners, historian Dr. Nina Gould and billionaire inventor Dave Purdue, to assist him in the mission to salvage not only the wreck but Dr. Malgas' withering career. Some other people Dr. Malgas hired for the expedition turn out to harbor secrets about their intentions and identities, each having their very own reason for joining the venture.
Once the mysterious wreck is located, Crystal Meyer, Purdue's financial partner on the excursion, summons one of her contractors from Egypt to bring his tug boat to join them in the Indian Ocean. But Crystal has a secret too, and an unfortunate turn of events turns a simple salvage operation into an open sea nightmare.
Between the secrets of the crew and the secret of the enigmatic ship they are trying to recover, matters escalate quickly, leaving Purdue, Nina, and Sam in a race against time before the dark secret of the ship takes them all to the bottom of the ocean.
Of all the secrets, the Seventh Secret is the deadliest....
