"Hey, wanna see something kinda cool? I keep it in plastic because it's supposed to keep it safer and... well you'll see"
"It's a replica of the Mona Lisa?"
"No... not a replica, this is the Mona Lisa. It was stolen from the Louvre in 1911 and they never got the right one back."
"You're shitting me."
"No, seriously, I'm not kidding. My great grandfather ran an art gallery. It passed through his hands while it was missing in 1911, and he switched it with a copy."
"Come on, that's crazy. You're not serious."
"Look at this tiny stroke of green here. You won't find this on the one at the Louvre but you can just make it out in a few pre-1911 photographs of the Mona Lisa."
"Wait, so you're like... a multimillionare? Aren't the police looking for this?"
"As far as anyone in the art world is concerned, it's in the Louvre. Who's looking for it? I can't sell it, I'd have to return it to the museum. And who'd really be better off? It's not like the guys at the Louvre are going to be thrilled to find out they've been displaying a fake for 100 years and no one noticed."
"......"
"Don't tell too many people about it, okay? I don't want to get any awkward calls from anyone."