Detective Peter Pux stood in the abandoned warehouse, his gun drawn as he faced off against the collector. The man was tall and thin, with a cold, calculating look in his eyes.

"Hand over the Mona Lisa," Peter said, his voice firm. "This is your last chance."

The collector chuckled. "You think you can just walk in here and take it from me?" he said. "You have no idea who you're dealing with."

Peter's grip on his gun tightened. He wasn't about to back down now. He had come too far in this case, and he wasn't going to let the collector get away with the theft.

"I know exactly who I'm dealing with," Peter said. "A thief and a criminal. And I'm going to make sure you pay for what you've done."

The collector sneered. "You have no proof," he said. "You have no case against me."

But Peter was ready for this. "We have the Mona Lisa, and we have The Middleman's testimony," he said. "You're going down, and the Mona Lisa is going back where it belongs."

The collector's expression turned to one of defeat. He knew he had been beaten.

"Fine," he said, reaching into his pocket and pulling out the Mona Lisa. "Take it. But you'll never catch all of us. There are more of us out there, waiting for the next big score."

Peter took the Mona Lisa from the collector, a sense of satisfaction washing over him. He had solved the case and brought the thief to justice.

"We'll catch them all," he said, cuffing the collector and leading him away. "One case at a time."

With that, Peter returned the Mona Lisa to its rightful owner, and the case of the missing painting was finally solved.