In the television adaptation of 'The Testaments', a key narrative adjustment involves the character of Daisy, portrayed by Lucy Halliday. The series reimagines Daisy as an undercover agent operating within a Gilead finishing school, under the guidance of June Osborne, played by Elisabeth Moss. This creative decision allowed for Moss's celebrated return to the franchise, a development meticulously kept under wraps until the series debut. The character's codename, 'Danielle', further served to maintain secrecy regarding her pivotal role.

A significant departure from Margaret Atwood's source novel is the alteration of Daisy's lineage and age. In the literary version, Daisy is June's second daughter, known to 'Handmaid's Tale' viewers as Nichole/Holly. However, the show's creative team, led by Bruce Miller, opted to set the sequel only four years after the events of 'The Handmaid's Tale', rather than the book's fifteen-year leap. This compressed timeline necessitated a redefinition of Daisy's character, aligning her age more closely with Agnes, June's first daughter (played by Chase Infiniti). Despite not being biologically related to June or Agnes in the series, Daisy retains the inherent fighting spirit characteristic of both June and Agnes.

Miller, drawing lessons from his experience with 'The Handmaid's Tale', emphasizes his commitment to a satisfying conclusion for 'The Testaments'. He envisions a narrative arc spanning approximately 30 to 50 episodes, translating to three to five seasons. The initial season focuses on the characters' 'awakening' to their harsh realities, with subsequent seasons delving into self-discovery and deeper understanding of their identities within their world. Miller confirms that the storytelling mechanism, often involving voiceovers, implies the survival of the narrating characters, though acknowledging the universal truth that life itself is finite.