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.

Late summer, 1940. Hitler has conquered France. Now he intends to cross the Channel and defeat Britain before winter arrives. A group of young refugees led by British spy Charles Henderson faces a stark choice: to head south into the safety of neutral Spain or go north on a risky mission to sabotage the German invasion plans. For official purposes, these children do not exist.

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 12-year-old French orphan. The British secret service is about to discover that kids working undercover will help to win the war.

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, 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.