The police find out that Berlin's real name is Andrés de Fonollosa and that he is terminally ill during part 1.

Despite his death, he appears in a main role in part 3 through flashbacks to several years earlier, showing his original planning of the Bank of Spain heist and being married to a woman named Tatiana.

La Voz de Galicia characterised Berlin as a "cold, hypnotic, sophisticated, and disturbing character, an inveterate macho with serious empathy problems, a white-collar thief who despises his colleagues and considers them inferior".

[9] The family connection between the Professor and Berlin was not in the original script, but was built into the characters' backstory at the end of part 1 after Morte and Alonso had repeatedly proposed to do so.

[10] The writers decided to bring Berlin back for flashbacks in part 3, as they felt the character had gone through a sufficient redemption arc and was popular with the audience.