One day Isaac accidentally came to know that Chance and Lucas were assassins, and that David too is indirectly involved in this field.
That day Lucas was terrified, not because they were assassins but because he thought he would lose a close friend forever as it is a dangerous field.
Isaac loved his friends more than anyone else.
Although he was affected by this truth, but eventually he made peace with it and accepted his friends the way they were.
Jack and Carol were unaware of the truth so Isaac was careful and mindful of his actions and he too promised to hide this truth from them.
Isaac had his own business and commitments but he used to ensure to spend some time with his friends.
But after Lucas' death and Carol's rejection, Isaac was broken and distanced himself from the gang for a while.
