Max Heald is an agent for British Intelligence.
Heald works for a secret branch of British Intelligence under the strict control of Jonathan Mortimer. While there is a reasonable amount of respect between the two men, there is no doubt who is the boss. Still, Heald is not above thumbing his nose at the boss when he is riled and Mortimer wouldn't sway from sending Heald to his death if the mission called for it.
Heald has been an agent for Mortimer for many years, probably starting to work for him during the Second World War operating behind the lines. When the War ended, Mortimer's position in Intelligence transitioned to become a small, little known agency run by him from a nondescript office marked with a simple "Importer" sign on the door. Heald was one of those to go with him.
Now, a decade and half later, Heald, certainly in his late 30s or early 40s, operates largely in Europe where his knowledge of languages, French, German, and Russian to name three, has made him able to blend in everywhere in that continent. He has been shot at and shot and he has shot back on many occasions.
The biggest problem facing Heald within the Intelligence community is his wife, a fellow agent he married around five years ago and who, three years before the first book suddenly disappeared from England and showed up in Moscow soon after, revealing she had been a double agent for many years. Reeling from the betrayal while still in love with and deeply missing her, Heald expected to be released as a security risk but Mortimer kept him on.
The principle opponent that Heald faces in his adventures is the Soviet Section 9 of the MVD, a division dedicated to the elimination of enemies.