While on a grand world tour, The Muppets find themselves wrapped into an European jewel-heist caper headed by a Kermit the Frog look-alike and his dastardly sidekick.
For the plot to work, we're supposed to believe that Kermit and Constantine look so alike that no one can tell them apart, but also that nobody notices they look alike at all. This is sort of like very very obvious gaslighting.
Kermit is framed for robbery and sent to jail, but he is not kidnapped. In the final scene the main antagonists takes Ms. Piggy as a hostage to escape.
Though a subplot does follow Sam Eagle and a man in the Interpol. Very played for laughs, can't be taken seriously. I'm waiting for their Disney+ spinoff to get greenlit, personally.