Signal

 Detectives from the present and a detective from the past communicate via walkie-talkie to solve a long-time unsolved case.

1. You're Doomed

2. We Still Have a Chance

3. We Can Prevent the Killings

4. We Found the Killer

5. Changing the Past Alters the Present

6. Catch Him by All Means

7. We Must Dig Deeper

8. How Are You Alive?

9. Hongwon-dong Case

10. Someone Has to Stop the Bad Guys

11. The One Last Case

12. The Case Was Manipulated

13. The Real Assailant

14. Not Now, but Maybe in the Past

15. Is It Really You?

16. If You Don't Give Up

Melodu