Why did the knights enter the cathedral at Canterbury?

Question

This is in chapter 9 activity 1 in the world history workbook. 

Answer 1

Assume you are referring to the murder of Thomas a Becket.

Henry II was vexed that Thomas had become more interested in religion (the poor) than begin the King's chancellor (he resigned.)

Supposedly Henry said "Will no one rid me of this man?"

The knights did.