"We Were Liars" is a based on a novel by E. Lockhart about a wealthy family, the Sinclairs, and their summer home on a private island, known as Beechwood Island. The story centers around Cadence Sinclair, who, along with her cousins Johnny and Mirren, and family friend Gat, form a group they call the "Liars". The story explores themes of family secrets, deception, and a mysterious accident that changes Cadence's life.