Every summer, Cadence Sinclair cherishes her time with her cousins Mirren and Johnny and her best friend Gat on Beechwood Island; at sixteen, their summer mischief transforms when Cadence and Gat fall in love, while adult tensions rise in her family.

Following her mysterious accident, Cadence suffers a year of illness, amnesia and loneliness, having had no contact with the Liars; returning to Beechwood for answers, the island begins triggering memories of Summer 16.

As the Sinclairs prepare for a quiet Fourth of July, Cadence investigates one of the Liars, uncovering memories of last year's crowded celebration; Cadence discovers a shocking truth about a Liar, leading to a confrontation.

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 the Sinclairs.

Unable to continue keeping secrets from her, Gat finally opens up to Cadence about his perspective on the island; Gat recounts his memories of an honored Sinclair tradition, Tipper's Lemon Hunt, and the unplanned visit from his mother.