A Matter of Honour - Jeffrey Archer

It seems innocent enough. A disgraced British colonel bequeaths a mysterious letter to his only son. But the moment Adam Scott opens the yellowing envelope, he sets into motion a deadly chain of events that threatens to shake the very foundations of the free world.

Within days, Adam's lover is brutally murdered and he's running for his life through the great cities of Europe, pursued not only by the KGB, but by the CIA and his own countrymen as well. Their common intent is to kill him before the truth comes out. While powerful men in smoke-filled rooms plot ever more ingenious means of destroying him, Adam finds himself betrayed and abandoned even by those he holds most dear.

When at last he comes to understand what he is in possession of, he's even more determined to protect it, for it's more than a matter of life and death-it's a matter of honor.