It’s the start of a new week for the team of intrepid postal detectives tasked with tracking down the recipients of undeliverable mail. Amongst the hustle and bustle of shuffling letters, Oliver O’Toole (Eric Mabius), the rigid leader of the team, makes his way to the office. As he moves through the mailroom, he bumps into department newcomer and resident technophile Shane McInerney (Kristin Booth). As Oliver and Shane arrive at the dead letter office they are greeted by the free-spirited, “girl next door” Rita Haywith (Crystal Lowe) and the nerdy but lovable Norman Dorman (Geoff Gustafson).

It’s a particularly special day at for the dead letter team as they prepare to welcome their new supervisor, the legendary Theresa Capodiamonte (Valerie Harper)! As 6-time recipient of the prestigious ‘Dark of Night’ award, Theresa Capodiamonte is a legend in the postal community. The once aspiring Broadway performer followed the dreams of her father, joining the postal service and working her way up to becoming a “goddess in the postal Acropolis.” From the moment she walks into the office, her larger-than-life personality captivates the team. Theresa is also a former colleague of Oliver’s grandfather. A postal legend in his own right, the memory of Oliver’s grandfather is an unseen hand, inspiring Oliver to maintain the highest standards in postal excelence.

With the team assembled and their new supervisor in place, it’s time to get down to the work of delivering lost letters. Oliver selects a letter addressed to ‘Gramma’ at the ‘Lend Him Her Manners.’ The letter also includes a child’s drawing, presumably of the author and his grandmother, standing in front of two trees with a wind chime hanging from one of the branches. There is also a message, “P.S I’m bringing more spoons so we can make another one.”

With just these few details to go on, the team almost immediately discerns that the letter is intended for one of the presumably many ’Grammas’ at the Lendimer Manor Retirement Home. The letter goes on to say that since ‘Gramma’s’ birthday is the next day, and since he’s “pretty sure the retirement home is just down the road,” he’s going to sneaking out of his house and ride all night until he gets to ‘Gramma’s’ retirement home. The author closes the letter by saying that ‘Gramma’ “has to call him Owen now.”

Based on what they’ve determined, the dead letter office team head to the Lendimer Manor Retirement Home to find Owen’s ‘Gramma’. At the home the team finds a few “Babbas,” “Bubbys,” “Grammys,” and “MawMaws” but no “Grammas.” The team approaches Donna, the activities director at the home, for help at whittling down the search. Donna leads the team to the music room where they find a group of “Grammas” rehearsing for an upcoming musical cabaret. As luck would have it, one of the “Grammas,” Vivian, has a birthday the tomorrow. But instead of being happy, Vivian is clearly agitated by the attention and is adamant that she doesn’t know anyone named Owen. Vivian refuses to accept the letter and sends the Oliver and the team away.

At lunch with Theresa, the team can’t escape the feeling that Vivian is in fact their missing “Gramma.” After analyzing the clues they realize that Vivian was doing all she could to avoid talking about her family in front of Donna. It’s then that it becomes obvious that Vivian isn’t forgetting her grandson, but that she’s protecting him. But from what?

The team runs back to the retirement home, but this time, they do everything they can to keep Donna occupied while they talk to Vivian. While Rita distracts Donna, Oliver and Shane confront Vivian one-on-one. It’s then that Vivian reveals that her grandson’s real name is Casey and that she doesn’t know where he or his parents are. Casey recently witnessed the murder of a drug kingpin. Vivian reveals that terrible threats were made against Casey’s life and that if anyone found out where he was, his life would be in jeopardy. As a result Casey and his family were sent into witness protection until after he can testify at the trial. Shane immediately begins researching the case and even stumbles across a picture of the suspected murderer and his accomplice. Shane recognizes the accomplice as Donna, the new activites director at the home. The pieces of the puzzle are starting to fall into place and it’s clear that danger is a lot closer than anyone suspected.

With time ticking away, the dead letter team races to get intercept Casey before he makes his doomed bike ride to the retirement home. But on her way out of the home, Vivian gets cornered by Donna. Donna makes an unusual point of buttoning her coat and tightening her scarf. What Vivian doesn’t realize is that Donna also slyly grabbed the letter in Vivian’s pocket, containing all the information about Casey’s whereabouts.

Now that Donna has everything she needs to get to Casey, Vivian and the dead letter team move at break-neck speed to head her off. Luckily, Norman, with a little help from his real estate mogul cousin, is able to set up a diversion that sends Donna to the wrong house. Donna walks up to the home, gun in hand, and rings the bell. After no one answers, Donna peers into a window, seeing what appears to be an empty house. Realizing she’s been had, Donna attempts to run away. But before she can make a break for it, Oliver opens the door and the police pull into the driveway. A police officer orders Donna to freeze and put her hands up–she’s busted.

With Donna in custody, Shane, Norman, Rita, and Vivian frantically search for Vivian’s grandson. Just then, a squad car zooms past illuminating a little boy riding his bike. Vivian immediately recognizes Casey, jumps from the car, and runs to embrace him.

But all is not finished for the intrepid team of postal detectives. With Vivian reunited with her family, the Lendimer Manor needs a replacement for the musical cabaret. Enter Theresa Capodiamonte, who bravely takes the stage and fulfills her lifelong dream of becoming a Broadway performer…even if it is on a slightly smaller stage!