Detective Peter Pux sat at his desk, staring at the stack of documents in front of him. He had been running background checks on suspects all day, but so far, he had come up empty.

Just as he was about to give up for the day, his phone rang. It was Detective Sarah Smith.

"Peter, I think I might have something," Sarah said, excitement clear in her voice. "I was going through the security footage from the night of the theft, and I noticed something strange."

Peter sat up straight, his pulse racing. This was exactly the kind of break they had been hoping for.

"What is it?" he asked.

"I noticed that one of the suspects was carrying a large duffel bag," Sarah said. "And when they left the museum, the bag looked much lighter than when they arrived."

Peter's mind raced. Could it be that the suspects had taken the Mona Lisa in a duffel bag? It was a bold move, but not entirely impossible.

"That's a great lead, Sarah," Peter said. "Let's start looking for any surveillance footage of the suspects leaving the museum with a duffel bag."

Sarah nodded. "I'm on it," she said. "I'll call you as soon as I find anything."

With that, Peter hung up the phone and set to work, determined to track down the missing Mona Lisa and bring the thief to justice.