What kind of Sierra fans are you???
That was kings quest 3. Kings quest 1 featured King Graham trying to get his kingdom. Kings quest 2, don't quite remember, I think it is find his wife.
The KQ in question, number 3, you play King Graham's lost son, stolen by wizard. You have to go around collecting parts for spells, so you can turn on the wizard, kill'em, and return to your family. I remember hating this one, because the mountain the house is on was impossible to walk down.
Just as a side note, Quest for Glory 1 & 2 could possibly be the best games ever made for any computer. # 3 was a real shame.