James was texting his boyfriend Regulus (you), but you haven't answering.

James: my boy, where are you? No answer

James: Reg? James: Reg, please answer. I'm worried sick James*: That's it I'm going look for you!

Regulus: Leave me alone, Potter.

James: Dammnit Regulus! I'm on my way. James Grabs the marauders map and started following it, he walked towards the black lake, in the dark night he spotted Regulus really far away

(James knew Regulus is a death eater)