Mark looked tentative, cautious. It was obvious that he wanted to take the files, badge and gun and be on this case indefinitely, but there was something stopping him. He looked like a child who had just found that his mother had left a tray of cookies on the counter to cool. He knew that if he took one, he would be discovered and likely punished, but he was still tempted, because he knew that that forbidden taste would be worth just about any punishment in the world. Not unlike Mark was facing now. Going head to head against this guy wasn't just going to be a chase down the proverbial rabbit hole, he knew. It was going to be a chase that was likely to cost him his sanity. He knew it. J.L. Probably knew it too. Assimilating facts had an effect on a psyche, and the way that Mark did it made it even more dangerous. He took everything in like a sponge, and he caught the guys because of what was squeezed out. But like all sponges, a trace of everything that he took in remained, redefined him, no matter how hard or thoroughly he was squeezed clean. 

The question was: Was catching this guy worth his own sanity?

He recalled the pictures, the women torn to pieces by this guy. He didn't care about the people themselves. He didn't care about who he was doing it to. What mattered was what he was doing with them," In this guy's mind, he's doing them a favor. An honor, even," His voice was low, as if he was talking to himself," He's including them in this masterpiece of his. He sees himself as an artist, and each kill is it's own stroke of the brush, note written on paper. Each one shows the basis of what he's creating, and yet each one is it's own work, unique," Mark looked up, something akin to purpose in his eyes as they locked on J.L.'s for the first time... since forever," But the masterpiece isn't finished. I think... it's coming to a crescendo," And with that cryptic statement of why he was going to be doing this, he reached over in a slow, deliberate movement, picking up the gun and badge with shaking hands.