When Mark asks Tracy to marry him, she tells him about this brother she has. Evan has agoraphobia, a fear of open places, which she seriously feels could be a threat to her and Mark'srelationship. Mark, easy going and less of a worrier, doesn't foresee this, but when he meets Evan he develops a strong desire to cure him. Despite her devotion to Evan's welfare, Tracy nevertheless observes Marks endeavor as more hindrance than help. Which in turn makes Mark soon realize that she may be as much of a puzzle as is her brother. Arguments and small wars develop between the three of them amidst their learning about challenge, trust, and a clearer way of perceiving the truth.