Sara Oliver was a part of the squad that entered the Baruca Hill Correctional facility to break Simón Lago out of there. The character is played by Laia Manzanares.
Sara shows up with Lennon at the bar when he tells the others about the job that they just got. She is also tasked with placing the signal jammers and taking out the power to the facility.
It’s suggested that there is a specific reason she was a part of the squad that stormed the facility, which is revealed as the series continues.
She had inside knowledge
When Ruso asks one of the hostages about the passageway that leads to the Green Block, she claims it doesn’t exist. Ruso looks at Sara for confirmation and Sara nods in disagreement.
They go into the director’s office to find the floor plans and that’s when Sara picks up one of the folders and pulls out her own file from there. She was once an inmate herself at Baruca which is why she was aware of the passageway and knew the layout of the facility.
In the brief glimpse of her past, it was shown that she was an exceptional young girl but one day she lost her mind and slit her parents’ throats which is why she was admitted.
Her brilliant skills and intellect
Sara also displayed a certain proficiency in tech and had good intellect when it came to carrying out a plan. While she was in Baruca, she would play chess with Cherokee and regularly come out on top.
She tells Rey that she was the one who help the cops block the cameras in the hotel the night that he was framed. She claims that there is a backup and agrees to help him in return for a favour.
When Lennon gets her tab open, he sees that she has incriminating pictures of himself saved there and begins to doubt Sara’s intentions. This shows Sara’s ability to plan for all eventualities, although her reason for having those pictures isn’t revealed yet.