Surprisingly, Ertl was the daughter of a Nazi propagandist who had fled to Bolivia. She was raised surrounded by her family's Nazi friends, such as Gestapo chief Klaus Barbie, aka the "Butcher of Lyon", who British director Kevin Macdonald alleges orchestrated Guevara's murder.

Monika cut ties with her fascist family and grew closer to the Communist cause. She was deeply moved by Che Guevara's assassination in 1967 which led to her joining the National Liberation Army of Bolivia (ELN), which Che headed prior to his death.

Under her new nom de guerre, “Imilla”, she worked with Che's former comrades to hunt down his killer. In 1971, Monika arrived in the German city of Hamburg, where she looked for Pereira, who was working at the Bolivian Consulate.

Monika gunned down Che's killer with three shots to the chest. As she escaped, she left behind her purse, a wig, a revolver, and a piece of paper with the words "Victory or Death - ELN".

The killing was soon linked to her and the US-backed Bolivian dictatorship put a $20,000 bounty on her head. However, Monika successfully returned to Bolivia with more targets on her mind, including her family's Nazi friends.

In 1973, after several days of surveillance, CIA trained special units ambushed and murdered Monika in the capital city of La Paz. Her body was never found. Monika was dubbed “the avenger of Che”, a name that made headlines around the world.