In this scene, Prospero has used his magical power and his control over Ariel to tell the royal party that they have done wrong and that they will have to change their ways and repent.  What Prospero is trying to do, of course, is to get them ready to see him again.  He wants them to feel that they have done him wrong so that they will treat him well when they do see him.

I think the words that best show that his efforts have had an effect on the nobles are these:

My high charms work
And these mine enemies are all knit up 1670
In their distractions; they now are in my power;

Gonzalo confirms that Prospero's plan is working when he says

All three of them are desperate: their great guilt,
Like poison given to work a great time after,
Now 'gins to bite the spirits.

These lines of Gonzalo are right at the very end of the scene.