Crilly had been in school with Cal and in one year they had been in the same class together. He is a big lad for his age with large ears. Once somebody had said that he had ears like taxi doors so Crilly beat him up. Crilly has no compunction about beating somebody up. Cal thought very early that it was wise to be on the right side of him because Crilly could be nasty when he wanted. And with this tactics of intimidation he "convinced" Cal to join his group and also in this way he forces him to stay there.
Crilly never hurt Cal or did something like that but he knows that Cal is afraid of him and he exploits this fact without any scruple. He also doesn't shrink from robbing a shop or even from killing a person. He is an unscrupulous man who obviously is a member of the IRA.