Oliver is delighted that his team's new postal office supervisor is his late grandfather's famous former colleague, Theresa Capodiamonte. She can see his own excellence when they receive a cryptic letter from nine year-old Owen. The spelling and message didn't allow regular delivery, but Oliver's team works out it's to a rest home, presumably to his granny. They find her, but she denies and refuses the letter. Oliver realizes that's a ruse to protect the rascal, who in fact is Casey, key witness against a drug lord, in witness protection with his family, but doing a fugue to celebrate granny's birthday, and the presence of an undercover fiend.