Fatal caviar

"Ten thousand for a spoonful," Zhao Yu said to Zhang Menghai."If we solve this case, will you treat me to a meal?"

"..." Zhang Menghai thought for a moment and said honestly,"I can't afford it!"

"Caviar," Lei Dasheng recalled,"is there a problem with this caviar? We ... We all ate it!"

"Right, there's a big problem!" Zhao Yu said,"I asked the six of you, and five of you told me that you seemed to remember eating all the caviar!

"There's another one who said he doesn't remember at all.

"But," Zhao Yu pointed to the photo and said,"later, when the police took photos of the scene, there was still some caviar left on the plate!

"From the photo, it's at least enough for one person, right?

"This is interesting. If you've already finished the caviar, why is there an extra serving on the plate?"