Tuur and Lambert are best friends in a Nazi-occupied Dutch village who pass their days playing soldiers and exploring local caves, mimicking a war that seems far removed from their everyday life. When Maartje joins their class, the young girl immediately stands out as different from her classmates. Yet the boys embrace their new friend, forming a unique bond based on shared adventures, secrets and mischief. Ultimately, the realities of war find even them - Lambert's father, a Nazi sympathizer, is named mayor of their town and Tuur discovers his own father and brother have joined the resistance, instantly putting the two boys at odds. Meanwhile, Maartje is hiding a secret of her own, one that not only threatens to tear the new friends apart, but could lead to devastating consequences for anyone involved in keeping it. Secrets Of War puts both the danger and the humanity of wartime friendships squarely on the shoulders of three children who must face extraordinary circumstances with a maturity far beyond their years.