Rework: When a witness in custody and two cops are killed, the Homicide Detective must solve a piracy case to catch the killer and the mastermind. Thriller? Crime? Drama? Sci-Fi? Not sure…

This is mostly unclear. What is the relation between a piracy case and the triple murder? There is no logic connecting these elements directly. Furthermore, if he or she is a detective he or she are just doing their job, what makes it unique or interesting? Where is the hook?

We can fundamentally polish this...

After two cops and their witness are assassinated, a detective's investigation leads him into an undercover ring of piracy controlled by a ruthless murderer.

But we still need to spice up the detective, this piracy operation and even the murderer somehow, or else it risks sounding ordinary.