Carrasco had planned with the priest and the barber to let Quixote leave on his sally and to force him back home through the trick described above: he would disguise himself as a knight, challenge Quixote, and make him return to the village. Now that the trick has failed, Carrasco wants to play a second trick on Quixote to take his revenge.
Had Carrasco’s plan worked, Quixote would have been defeated by his own shadow– his own double. The false, theatrical version of him would have prevailed. Fortunately, it is the real Quixote who prevails, so he marches bravely on.