From working class roots, a former telegraph messenger boy comes to guard one of Britain's most flamboyant and controversial politicians. Walter doesn't serve long before he counters the first deadly threat to Churchill - IRA gunmen lurking on the route to Whitehall.
Walter accompanies Churchill to the Cairo Conference, which shapes the future of the entire Middle East. In their travels, they face rabid, rock-throwing crowds and meet Lawrence of Arabia - the one man who commands enough respect to shepherd them to safety.
Churchill's resistance to self-rule in India makes him a target for terrorists. Under this ominous cloud, he and Walter set off on a lecture tour of the States. But when danger finally strikes, seriously injuring Churchill, it comes from an unexpected and far more mundane quarter.
Resuming his tour after his convalescence, Churchill wins the hearts of Americans everywhere he goes. Not everyone is so in thrall, however. The Indian secret societies still stalk him and come uncomfortably close to carrying out their deadly plan.
With the Conservative Party driven from power, Churchill enters his "wilderness years". Nevertheless, his outspoken opposition to the Nazis earns him Hitler's lasting fear and enmity. In the run up to war, Hitler's assassins attempt a preemptive strike on the English politician who harbors no illusions about Germany and would stand up to the Führer.
After returning to government and leading the Admiralty, Churchill ascends to the Prime Minister's post on the very day that Hitler invades the Low Countries. He immediately embarks on an aggressive campaign of personal diplomacy. Much to Walter's worriment, his travels include six trips to France on flights well within range of Luftwaffe fighters.
The early days of the war bring some of Churchill's most difficult - and dangerous - decisions. As bombs rain down on London, the Prime Minister stubbornly insists on walking the streets among the people, watching air raids from rooftops, and visiting anti-aircraft battalions, with only Walter to protect him from the terror above.
Bunning a gauntlet of U-boats in the North Atlantic, Churchill and Walter set sail for America in an unescorted ship to plot Allied strategy with Franklin Roosevelt. Disaster comes closest, however, as the Prime Minister prepares to board a flying boat for the trip home and a crazed gunman lurks nearby.
In 1942, Churchill crisscrosses North Africa and the Middle East and confers with Stalin in Moscow - logging much of the 200,000 miles he would travel during the war, under constant threat from assassins and Axis aircraft. In one instance in Algiers, General Dwight D. Eisenhower resorts to deception to keep Churchill safe.
After two Atlantic crossings and two troops across the length of the Mediterranean, Churchill grows increasingly frustrated with Roosevelt and suspicious of Stalin. When the three leaders meet in Tehran in 1943, the Germans launch Operation Longjump - a plot in which elite commandos parachute into the city, bent on assassination.
Returning from the Tehran Conference, a sick, exhausted, disheartened Churchill survives his darkest night, with Walter keeping vigil at his bedside. Could Churchill have died of pneumonia that night in Tunisia?
Only months after the D-Day invasion, the desperate Reich answers with a terrifying new weapon - V-2 rockets screaming into London. The stress affects even Churchill's normally unshakeable bodyguard, who spends weeks in a convalescent home. At a conference in Athens, however, the threat comes not from above, but from below, as security forces uncover a ton of explosives secreted near Churchill's hotel.
VE Day brings relief to the country but no respite for Walter. Jubilant crowds clamouring to touch their heroic Prime Minister pose almost as great a security risk as Nazi assassins had. Only later does Walter have the opportunity to reflect on his nearly 20-year relationship with the employer who had become his friend.
