Herge might have had taken some time off during the writing of the "Land of Black Gold". Here he is shown arrested by his own characters and forced back to work to finish the story. I cannot read what Segneur Oliviera da Figuera is saying, but the rest are loosely translated as follows (clockwise, from the left):
Haddock: "Blistring barnacles! You must fill these pages fast, dude!"
Oliviera:"..." [something about the servants of Professor Smith].
Thomson: " No more fun, my son! Back to work!"
Dr. Mueller: "Damn, he is going to send Tintin after me again!..."
Thompson: "To be precise: No more sun!"
Emir Ben Khalish Ezab: "Are you finally going to let Tintin rescue my darling Abdallah?"
Tintin: "That's right, my firends! Herge has been found! We are finally going to know the rest of "The Black Gold""!
Snowy: "How upsetting! I was quite enojying the break! He will be sending me again on new adventures"
Calculus: "I always said that you would find him if you look towards the west..."