The Shroud tells the gang that there are some supernatural beings, the Undead, who seek to hunt them down. Costa discovers the tunnel the boys found, which makes him suspect that someone from the town is a possible captor.

The boys are left without allies so Javi decides to look for the Undead at the town fair and follow them to his sister. Olivia discovers her grandmother's red notebook and begins to feel a supernatural gift awaken in her.

Javi and the gang chase a ghost to try to find out where the girls are being held. Javi manages to convey information to his father, but the Undead come forward with a masterful move.

The Undead deceive everyone by making a false revelation. The boys make a great discovery at the Aigües de Busot Spa. Costa discovers that the cases of three missing minors happen every three years in Levante.

Costa, Mario and Roca, Bea's father, receive very important information that guides them to the Spa. There everyone will discover something that can change their destinies forever.