When devoted husband Oliver sets out to plan the perfect surprise birthday party for his wife, Claire, he enlists the help of her longtime best friend, Freya. As the two work together in secret—coordinating decorations, guests, and heartfelt memories—an unexpected emotional connection begins to form. Late nights and shared laughter slowly blur boundaries, and what starts as an innocent collaboration spirals into a dangerous affair. As the party approaches, secrets simmer beneath the surface, threatening to explode and change everything. Behind the Balloons is a tense and emotional story about love, betrayal, and the cost of crossing lines that should never be crossed.