The day Aaron finished rehab, Cassie picked him up and drove him to New York City. Though they lived in Boston, and the facility was north, in New Hampshire, it seemed obvious to her that Boston was no place to celebrate, if celebrate was the right word. For one, it was Boston, and second, it was the site of Aaron’s most recent bout of trouble. Even if they would be returning soon enough, it seemed to her a kindness to prolong the time away as much as possible. New York, she knew, had its own “triggers”—even if Aaron claimed…