La Casa De Papel

The Professor: Um, no I uh haven’t seen your fork.

(Berlin returns from bathroom and slams bloody fork down on the bar)

Berlin: The meatballs and bow tie pasta didn’t settle well with me.

Ok hear me out.

Raquel and Sierra used to be lovers back in the day but their relationship went sour as they progressed through training. Ambition and jealousy got in the way of their affection towards one another (mostly from Sierra since she was so cut throat and envious of Raquel’s innate ability to negotiate whereas Sierra had to work hard to succeed).

This scene is proof, seeing as when Raquel takes Sierra’s hand there is no longer chemistry or that spark like there used to be between them. This explains Sierra’s warning that Raquel’s current relationship with the Professor will become meaningless in time. She warns that one day Raquel and the Professor’s love will fade into nothingness.

Their story is a tragic one since Raquel ended up in an abusive marriage and Sierra’s husband died. This is why Sierra is so bitter about the Professor and Raquel’s relationship, because she wants what they have. She misses Raquel despite everything that happened to them. She wants her Raquel back and if that means killing the Professor, then so be it, hence the ending of part 4.