The rules were simple: you walked up to the black box and chose which button to press. Either the red one or the blue one.The red one would mean you were going on a trip to visit a cake factory.The blue would mean you were going to the cup final.But when it was his turn, Noah saw something unexpected.There was a red and blue button, but also a third, green button.Nobody else had seen a green button. Even his teacher could not see one when she turned the box around.What did it mean.Was he imaginging it?What would happen if he pressed it?