Not all mail makes it to its intended recipient, so what happens to undeliverable mail? Several postal workers work as detectives to track down the people who never got letters and packages that were sent to them. The workers head out of their office to deliver mail that can save lives, solve crimes, reunite old loves and change futures. The group includes leader and charming postal detective Oliver O'Toole, technophile Shane McInerney, free-spirited Rita Haywith, and master researcher Norman Dorman. Together, they work to get the mail to its destination, and although late, in some respects it often gets there at just the right time.