In an interview with Variety, showrunner Michelle Paradise divulged the intricacies behind the rewriting of the final episode of "Star Trek: Discovery" to serve as a series finale and how it tied back to the Short Trek titled "Calypso." Originally slated to end with Burnham and Book conversing on a beach, Paradise knew right away that the episode needed a more conclusive ending once it became the series finale. What that ending should be took a little more time to become clear. 

With only eight weeks to execute the rewrite and a modest budget allowing for just three days of production, the team faced significant constraints. However, the Short Trek titled "Calypso" offered a narrative lifeline. This standalone episode, which streamed between the show's first and second seasons, hinted at a connection with Discovery's endgame, leaving a tantalizing thread to explore.

"We always knew that we wanted to somehow tie that back up," Paradise explained. "We never wanted ‘Calypso’ to be the dangling Chad." 

The intent was clear – to honor the promise made by "Calypso" and provide closure to its enigmatic narrative.

Paradise and co-writer Kyle Jarrow meticulously crafted a resolution that would seamlessly integrate with the existing storyline. The Discovery is restored to its 23rd-century state, and Burnham communicates with Zora, the sentient computer introduced in "Calypso," before embarking on a new journey. The scene is rich with intrigue, invoking Starfleet's enigmatic Red Directive protocols and hinting at a mysterious connection with the word "Craft."

Yet, beyond tying up loose ends, the focus remained on bidding farewell to the beloved characters. Paradise emphasized the importance of closure for both the audience and the cast, particularly for Sonequa Martin-Green's Burnham and David Ajala's Book. Prosthetic makeup aged the actors by 30 years, offering a glimpse into their characters' future and their enduring love.

The emotional weight of the farewell was palpable during filming, with Martin-Green describing it as "charged" and "emotional." Despite the intense schedule, which required round-the-clock work, the cast and crew embraced the opportunity to craft a poignant conclusion to their journey.

For Martin-Green, revisiting Burnham at the pinnacle of her life and career was a profound experience. 

"You just get to see this manifestation of legacy in this beautiful way," she expressed, reflecting on the character's growth over seven years.

Paradise echoed similar sentiments, stating that the condensed production schedule didn't hinder the final product. 

"I feel like it ends the way it needed to end," she remarked. 

The three-day shoot may have been grueling, but it ultimately delivered a fitting conclusion to Star Trek: Discovery's epic saga.