The literal translation of the original Spanish title is "Secret Origins," which makes more sense for the movie. But Netflix chose the English title "Unknown Origins."
New cop David (Javier Ray) is investigating a new and gruesome case. He turns to the older Cosme (Antonio Resines) - an excellent cop who is being retired by their new department head Norma (Verónica Echegui). Norma also forces David to work with Cosme's son Jorge (Brays Efe) who's a hard-core comic geek because each of the new murder cases seems to represent a comic book origin story, and David is disdainful of comics and knows nothing about them. We also find out that Verónica isn't big on the rules, and she loves cosplay (which she often does at Jorge's comic store).
The deaths they investigate are impressively grotesque, something I didn't enjoy. And I found the ending both inevitable and unsatisfying. Possibly interesting to fans of superhero stories who have a strong stomach.