Keller knew just as well as Neal did that the two were equal opponents in every aspect but one. Murder. That was where Neal Caffrey drew the line. Matthew Keller, on the other hand, didn't believe any such line existed.
The last con Keller and Neal had pulled together, was also the first time Keller killed someone.
The guy's name was Frank Olsen. He was useful during the whole operation, but also expendable. Keller had thought about it for quite some time and finally came to the conclusion that if he killed Olsen once they'd successfully gotten away, both Keller and Neal would make a much larger profit.
And so while they stood there in the warehouse, Keller pulled out his gun in one fast maneuver. It felt like he spent an hour pulling the trigger but in reality it was really only half a second.
Neal jumped and then his eyes dropped to the body to Keller. It was silent for at least a minute.
During this silence, Keller searched within himself for guilt or a sense of broken humanity... anything! But there was nothing. He felt no different than when Olsen had been alive.
"Keller! What the hell did you do?" Neal croaked finally.
"I... killed Olsen." Keller thought maybe if he said it aloud, he'd feel something. But he didn't. "We both make a much larger profit this way, Neal."
Keller remembered all too well the argument that followed. And then they had a falling out. They parted ways. Keller often looked back at this day and wished things could've turned out differently.
But they'd played out the way they had, and nothing could be done about it. Perhaps it was that argument that had led to the vicious rivalry they upheld today.
Recently, there'd been times Keller could've killed Neal. But he couldn't. Everytime he pointed a gun at him, he wasn't in any real danger. Because Keller just couldn't do it.
It wasn't just a partnership he'd lost in that argument. It was a friendship he could never forget.