Who is the hostage who becomes involved with the robbers in La Casa de Papel?

Monica Gaztambide is the hostage who becomes involved with the robbers in La Casa de Papel. She is the secretary of the mint director Arturo Roman and is having an affair with him. She is initially taken hostage by the robbers and held along with the other employees of the mint. However, she soon starts to develop feelings for one of the robbers, Rio, and begins to help them with their plan.

Monica changes her name to Stockholm while she is with the robbers, after suffering from Stockholm Syndrome. She plays a key role in the success of the robbery and becomes a significant part of the gang. Her involvement with the robbers causes problems in her personal life, including her marriage to Arturo Roman, who is also at the mint during the robbery.