Before he died, Gerry wrote Holly a series of letters that will guide her, not only through her grief but in rediscovering herself. The first message arrives on Holly's 30th birthday in the form of a cake and, to her utter shock, a tape recording from Gerry, who proceeds to order her to get out and "celebrate herself.” In the weeks and months that follow, more letters from Gerry are delivered in surprising ways, each sending her on a new adventure and each signing off in the same way: P.S. I Love You.

Holly's mother (Kathy Bates) and best friends, Denise (Lisa Kudrow) and Sharon (Gina Gershon), begin to worry that Gerry's letters are keeping Holly tied to the past, but, in fact, each letter is pushing her further into a new future.