How a German submarine sank a Canadian military hospital ship during the First World War and sparked outrage. On the evening of June 27, 1918, the Llandovery Castle--an unarmed, clearly marked hospital ship used by the Canadian military--was torpedoed off the Irish Coast by U-Boat 86, a German submarine. Sinking hospital ships violated international law. To conceal his actions, the U-86 commander had the submarine deck guns fire on survivors. One lifeboat escaped with witnesses to the atrocity. Global outrage over the attack ensued. The sinking of the Llandovery Castle was adjudicated at the Leipzig War Crimes Trials, an attempt to establish justice after hostilities ceased. The Llandovery Castle case resulted in a historic legal precedent that guided subsequent war crime prosecutions, including the Nuremberg Trials. Atrocity on the Atlantic explores the Llandovery Castle sinking, the people impacted by the attack, and the reasons why this wartime atrocity was largely forgotten.