Popular singer Silvia Sommer has a nervous breakdown on stage and is advised to take a nice long holiday in the Dutch Antilles. The moment she arrives on Curacao, she seems to remind a lot of people of someone else.
Sylvia bumps into a mysterious Dutchman know as 'El Loco', while looking for seashells on Bonaire. He too is startled by Silvia's resemblance to the girl called 'Alma'.
While Silvia is out for a drive in a rental car, she meets Lucas Achterberg, a biologist who specializes in snails. Unknown to both of them, two local men have been ordered to kidnap Silvia and are watching her every move.
Lucas begins to find out more about Sylvia's double, Alma Aures. Then both he and El Loco receive an omen of bad luck: a domino stone bearing two times four.
Feliciano, thinking he's already got rid of Lucas, now wants to meet El Loco face to face to get some answers. But El Loco and the others are expecting him, especially after Feliciano's henchman Marco turns against him.
El Loco presents Feliciano with proof that Sylvia and Alma are definitely two different people. The Lopez family has met another Dutchman on a plane: John van der Velde.
Lucas has figured out that Eddie is secretly searching for the location of El Loco's sunken boat, the Cucaracha. El Loco confesses to Sylvia that he was present when Alma drowned.
Eddie has invited John van der Velde along to search for the Cucaracha, but El Loco insists on diving himself. Meanwhile Lucas is tailing Laro and Chepito who are going after the Midalia in a speedboat.
