Pushing the characters into the social media age, the script will see Holly's sister ask her to retell the story of her letter hunt on a podcast - which will in turn, offer strength and guidance to widows embarking upon a similar journey.
But Holly isn't sure she can revisit the memories after grieving her husband.
The official synopsis reads: "When a group inspired by Gerry's letters, calling themselves the P.S. I Love You Club, approaches Holly asking for help, she finds herself drawn back into a world that she worked so hard to leave behind."
"Reluctantly, Holly begins a relationship with the club, even as their friendship threatens to destroy the peace she believes she has achieved," the statement continues.
"As each of these people calls upon Holly to help them leave something meaningful behind for their loved ones, Holly will embark on a remarkable journey one that will challenge her to ask whether embracing the future means betraying the past, and what it means to love someone forever."
Ahern first revealed that she has written the sequel in March, 2019 describing the project as a "deeply emotional" process.
"Postscript is the PS to my PS and while it is a sequel, it is also a story that stands alone about living a purposeful life in the face of illness, grief and loss," she said. "I hope that new readers and P.S. I Love You fans alike will embrace Holly's new journey."
Swank is sure to reprise her role but it has yet to be confirmed whether or not Butler will bring back that Irish accent.