When two former school friends unexpectedly cross paths after years apart, their reunion brings together a tight group of four long-term couples. What starts as a nostalgic dinner party quickly escalates when they decide to play a consensual "key game"—everyone drops their house keys into a central bowl, and whichever key each person draws determines who they spend the night with. Over the course of eight episodes, the experiment ignites underlying sexual tensions, unspools secret desires, and tests the fragile boundaries of each couple's relationship.