Milly, Aubrey, and Jonah Story are three estranged cousins who have never met their elusive grandmother, nor have they spent time together. Unexpectedly, they receive letters inviting them to spend the summer at her luxurious island resort, stirring a mix of surprise and intrigue within them. Despite the strange disinheritance that their parents faced, the trio is urged firmly by their said parents to seize this chance to mend fences with their wealthy matriarch. Upon arrival, however, the cousins quickly realize the resort bears more shadows than sunshine, hinting at a nefarious agenda and the grim secrets enveloping their family's history. As the summer unfolds, Milly, Aubrey, and Jonah inch closer to unravelling the web of deceit that split their ancestors apart and must brace themselves to face the unsettling truths that the island, and their grandmother, are ready to disclose.