Having remembered a family tragedy, Cadence presses The Liars for answers. Mirren reveals a crush gone awry, Johnny recalls an unwanted visitor, and Gat recounts their relationship's painful turn. Tension between the aunts continues to rise, and Cadence suspects at least one Liar is hiding something, questioning whether what happened last summer was an accident at all.

As the Sinclairs prepare for a quiet Fourth of July, Cadence investigates one of The Liars, uncovering memories of last year's crowded celebration. While the Sinclair sisters vied for their father's approval, The Liars navigated their romantic lives and Ed surprised Carrie. In present day, Cadence discovers a shocking truth about one Liar, leading to a confrontation as explosive as the fireworks.

Unsettled by a series of painful memories, Cadence tries to enjoy what's left of her summer – even if it means distracting herself with a potentially dangerous stunt. Despite her best efforts, she remembers a stormy day from Summer 16 when rising seas and frustrations threatened every Sinclair, exposing the family's darker side and forcing Gat and Cadence to confront their unspoken feelings.

More uncertain than ever, Cadence reluctantly joins Harris on an excursion, triggering memories of their final confrontation in Summer 16. During a tense family dinner, The Liars confront their mothers about family secrets. In the aftermath of shocking revelations, The Liars mourn their once-beloved childhood playground and unite in an attempt to save their fracturing family.

Cadence devises a plan to trigger her latent memories of the final hours before her traumatic accident, but she can't do it alone – she must convince the reluctant Johnny, Mirren, and Gat to help her, even if it means risking everything. But as the truth begins to come back to her in fits and starts, Cadence realizes that she, herself, has been the biggest Liar of all.