Summer, 1944. As Allied soldiers prepare to land in France, Marc and his friends must destroy a battalion of German tanks that could halt the invasion in its tracks. The tide of war has turned against the Nazis, but desperation has made them more brutal than ever. Henderson's Boys' final mission will be their most dangerous. With food and weapons in short supply, survival is the biggest challenge of all.

Spring, 1943. The war is turning against Germany, but Hitler isn't giving up. In a secret bunker deep in occupied France, scientists are hard at work on Hitler's latest deadly weapon: code name FZG-76. Back in England Henderson's boys will need to undergo advanced sniper training if they've any chance of infiltrating the bunker. Parachuting into occupied France, they track down a secret dossier filled with invaluable material — and uncover the meaning of the enigmatic code. For official purposes, these children do not exist.

One of Henderson's best agents is being held captive in Frankfurt. A set of forged record cards could be his ticket to freedom, but might just as easily become his death warrant. A vital mission awaits him in France — if he can find a way to escape.

Spring, 1941. German submarines are prowling the North Atlantic, sinking ships filled with the food, fuel and weapons that Britain needs to survive. With the Royal Navy losing the war at sea, six young agents must sneak into Nazi-occupied Europe and sabotage a submarine base on France's western coast. If the submarines aren't stopped, the British people will starve.

Britain, 1941. The government is building a secret army of intelligence agents to work undercover, gathering information and planning sabotage operations. Henderson's boys are part of that network: kids cut adrift by the war, training for the fight of their lives. They'll have to parachute into unknown territory, travel cross-country and outsmart a bunch of adults in a daredevil exercise. In wartime Britain, anything goes.

Summer, 1940. Hitler's army is advancing towards Paris, and millions of French civilians are on the run. Amidst the chaos, two British children are being hunted by German agents. British spy Charles Henderson tries to reach them first, but he can only do it with the help of a twelve-year-old French orphan. The British secret service is about to discover that kids working undercover will help to win the war. For official purposes, these children do not exist.

Charles Henderson is the last British spy left in occupied France in 1940, living on a farm near Calais with four runaway kids cut adrift by the war. He and his young agents are playing a dangerous game: translating for the German high command and sending information back to Britain about the Nazi plans to invade England in September, on Eagle Day. The RAF must destroy the Nazi invasion fleet, but Northern France is heavily defended and the camouflaged barges are impossible to target at night. Together, Henderson and his team hatch a daring plan to guide the British bombers to their target. Their lives are on the line, but the stakes couldn't possibly be higher.