It's nice to celebrate Father's Day with your family.
Dave has already planned a party with family for fathers day which is next week, when his boss asks him to work overtime that day.
Dave wants to answer his boss' request for overtime.
Dave tells his boss that while the money would be nice, family is more important, and he can't work.
Dave tells his boss that he'll be there as the boss needs him, and he's loyal to the company.
Dave's father is delighted to find out Dave will come to the party and spend time with him.
Dave's father is really hurt his son isn't there to celebrate fathers day, rendering it useless.