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In a vault at Yale lies a book of about 240 pages, written in a script that no one has ever been able to read, on parchment dated to the early 1400s. An emperor is said to have paid 600 gold ducats for it, a Prague alchemist called it a Sphinx, and the codebreakers of two world wars failed to crack it. We follow the book itself, the vanished trail of its owners, and the codebreakers, scientists and new studies still trying to unlock it.

On 31 October 1944, RAF Mosquitoes flew low across Denmark to hit a single target: the Gestapo headquarters inside the student dormitories of Aarhus University. In this deep dive: why the Danish resistance begged for the raid, how the attack was timed for the Gestapo's lunch break, the files that were destroyed and the resistance network they protected, and the remarkable escape of Pastor Harald Sandbæk from the rubble just before his interrogators could finish with him.

Near Xi'an lies the tomb of Qin Shi Huang, the man who united China in 221 BC. Archaeologists know where it is and have mapped it from outside, yet more than 2,000 years after his death the burial chamber has never been excavated. An ancient historian wrote that it holds rivers of mercury and crossbows set to fire at intruders, and modern scientists have found unusually high mercury in the mound. We follow the emperor who built it, the account and the evidence, the clay army found by farmers digging a well in 1974, and why China keeps the tomb sealed.

In November 1939 a carpenter named Georg Elser spent more than 30 nights locked inside a Munich beer hall, hollowing out the pillar behind Hitler's podium and hiding a time bomb inside it. On 8 November it exploded exactly as planned, 13 minutes after Hitler had left. We follow the lone man who nearly changed history: how he built the bomb, why Hitler walked out early, how he was caught at the Swiss border, how the Nazis blamed British spies they had kidnapped at Venlo, and how it took decades for Germany to accept that one ordinary man had acted alone.

In May 1940, Belgium's newest fortress guarded the bridges Hitler's army needed to break into the Low Countries. It was reputed to be impregnable. Then, at dawn on 10 May, silent gliders landed on its roof. We follow the secret plan, the hollow charge that had never been used in war, the commander whose tow rope snapped over Germany, the sergeant who led the attack in his place, the race for the Albert Canal bridges and the long night before the fort surrendered, and we hear what the raid meant for Belgium and for every airborne operation that followed.

In October 1942, a small Norwegian fishing boat named Arthur sailed into Trondheimsfjord with forged papers, a cargo of peat and two British Chariot human torpedoes hidden underneath. Their target was Hitler's biggest battleship, the Tirpitz. In this deep dive: Leif "Shetlands" Larsen and the Shetland Bus, how the crew bluffed their way past a German inspection, how the chariots were lost just 10 miles from the battleship on 31 October 1942, the desperate escape to Sweden, and the fate of Able Seaman Bob Evans.

On the night of 22 to 23 October 1943, as RAF bombers headed for Kassel, German night fighter pilots heard something strange on their radios: a second controller, speaking perfect German, giving them the wrong orders. In this deep dive: how the RAF used German-speaking operators in England to impersonate Luftwaffe ground controllers, the famous moment a German controller shouted that "the Englishman is now swearing", how the Germans switched to female controllers and Britain answered with German-speaking WAAFs, the fake fog warnings that sent fighters home, and how radio deception helped save Allied bomber crews.

On 5 November 1940, Convoy HX 84, 38 merchant ships with a single escort, the converted liner HMS Jervis Bay, ran into the German heavy cruiser Admiral Scheer in the middle of the Atlantic. In this deep dive: how Captain Edward Fegen turned Jervis Bay straight at the raider so the convoy could scatter, the Victoria Cross he won, how the Swedish ship Stureholm came back for survivors, and the tanker San Demetrio, abandoned on fire, found again by her own crew, reboarded and sailed home without charts or radio, followed by the salvage court case.

On 25 October 1944, a handful of small American escort carriers, destroyers and destroyer escorts found the battleship Yamato and Admiral Kurita's fleet bearing down on them off Samar. In this deep dive: how Halsey's fleet was lured away at Leyte Gulf, how Commander Ernest Evans took USS Johnston straight at the enemy, why USS Samuel B. Roberts became "the destroyer escort that fought like a battleship", how pilots kept diving at the Japanese fleet with empty guns, the loss of Gambier Bay, and why Kurita turned back.

In October 1942, weeks before the Allied invasion of North Africa, US General Mark Clark slipped ashore in Algeria from the British submarine HMS Seraph for a secret meeting with pro-Allied French officers. This is the story of Operation Flagpole: the flight to Gibraltar, the folding canoes and British commandos, the meeting at a farmhouse near Cherchell, the police raid that sent the Americans into a wine cellar, the general who lost his trousers and his gold in the surf, and the dangerous escape back to the submarine.

On the night of 18-19 December 1941, six Italian divers riding manned torpedoes, nicknamed "pigs", slipped into Alexandria harbour through a gate the British had opened for their own destroyers. By morning, the battleships HMS Valiant and HMS Queen Elizabeth were sitting on the harbour floor. In this episode: the submarine Scirè and its secret cargo, the diver Luigi Durand de la Penne held prisoner right above the bomb he had planted, the warning he gave Captain Charles Morgan minutes before the blast, Admiral Cunningham's cover-up with bands and ceremonies on deck, and the medal ceremony in 1945 that nobody saw coming. Unlocking the Unknown: true stories of WWII raids, deception and secrets. Short versions on our YouTube channel, Unlocking the Unknown.

During World War II, Allied forces employed innovative tactical deceptions—such as Operation Bodyguard, Operation Taxable, Operation Glimmer, and Operation Titanic using Rupert dummy paratroopers—to mislead German defenders regarding the true timing and location of the Normandy landings. These operations relied on radar countermeasures like Chaff (Window) and Moonshine to simulate phantom invasion fleets and airborne threats, successfully confusing German commanders and delaying critical reinforcements. At the same time, the de Havilland Mosquito, affectionately known as the 'Wooden Wonder', became one of the Axis's most feared Allied aircraft. Constructed primarily from wood due to aluminum shortages, the Mosquito possessed exceptional speed and low electromagnetic reflectivity, which consistently confounded German Freya and Würzburg radar operators. Together, these sophisticated electronic deceptions, tactical feints, and high-performance aircraft crippled German air defenses and significantly contributed to the success of the Allied invasion.

On the night of 15 October 1946, hours before he was due to hang, Hermann Göring bit into a cyanide capsule in the most closely guarded cell block in Europe. Eighty years later, nobody can say for certain how he got it. We examine the official investigation, the American lieutenant who received his gifts, and the former guard who claimed in 2005 that a girl named Mona tricked him into delivering it.

On 14 October 1939, a single German U-boat slipped through a gap in the defences of Britain's "impregnable" fleet anchorage at Scapa Flow and torpedoed the battleship HMS Royal Oak at anchor. 835 men and boys died in minutes, and the raid shook Britain six weeks into the war. We follow Günther Prien and U-47 in, the mistakes on board Royal Oak, the spy legend that grew afterwards, and the war grave that still lies in Orkney today.

During World War II, the British military employed ingenious visual deception and stagecraft to mislead the Axis powers. A notable figure in these operations was Jasper Maskelyne, a famous stage illusionist who joined the Royal Engineers and utilized his expertise in theatrical misdirection. Alongside specialized units like the Camouflage Directorate, also known as the "Magic Gang," Maskelyne helped construct elaborate decoys, fake tank armadas, and camouflage systems to protect strategic locations such as the Suez Canal and Alexandria Harbour. While historians continue to debate the exact boundaries between factual military records and Maskelyne's own embellished memoirs, these creative ruses—exemplified by Operation Bertram—successfully confused enemy reconnaissance. Ultimately, the combined efforts of artists, engineers, and magicians proved that intellectual misdirection and clever camoufleurs were just as vital to Allied victory in the desert as raw firepower.