Danny, after getting burned in a previous relationship, decides to avoid commitment by telling every girl he hooks up with that he's married. But when he meets a gorgeous young girl named Palmer, he thinks she could be the one until she finds out he's "married".
So in order to keep their relationship still going, he tells her that he and his "wife" are getting a divorce. When she insists on meeting her, he asks Katherine to pose as his wife. Katherine takes a call from one of her children, Palmer assumes that they're Danny's so wants to meet them.
And it's at this meeting that Katherine's son tricks Danny into taking them all on a trip to Hawaii.