Thomas 'Doc' Palfrey is an agent of Z5.
He is also the grandson of the second head of this international intelligence organization and the son of that man's daughter, Marion, now Z5's indomitable head. If having to live up to the legacy of one of the world's greatest unsung heroes, Dr. Stanislaus Palfrey, a man who helped mankind through an incredible array of catastrophes and quietly averted twice that many from happening, it is nothing compared to being reared by a woman with such a powerful personality. Most would have been crushed under such weight for having perfection expected in every endeavour can get to anyone. Tom Palfrey, though, was not just anyone.
Z5 is not just any intelligence agency, either. As described in one of the passages, Z5 "left politics to politicians, security to security forces, policing to police forces, and petty crime to the petty criminal" while it chose to focus on "megalomaniacs - terrorists, business tycoons and politicians - whose aim was to blackmail the world into dancing to their tune." To accompany this, it is set up as a non-profit trust with all money it makes going into running costs, though how it makes the money in the first place is not mentioned. Its agents, however, are largely members of their personal country's military or special police forces, seconded to Z5 as needed without strings attached.
Leading Z5 is Dame Marion Palfrey, an "elegant, head-turning widow in her fifties". She is a tough minded as it comes, a necessity when she is constantly having to send her operatives into harm's way even as she must fend off governments and high-powered people who would like to ignore Z5 sovereignty for their own power plays. Just as her father before her and Z5's founder, the Marquis of Brett, before him, she can stand up to the pressure only by never giving an inch.
That severity works its way to dealing with her head-strong son. At twenty-nine at the start of the series, he had first earned a PhD in a subject very dear to him, marine biology, then chose to serve in the military with the 16 Air Assault Brigade, even when it meant tours in Afghanistan.
Independent, fearless, perhaps impulsive, and determined to go his own way, he served with distinction until an attack saw shrapnel take out his left leg. Subsequently fitted with a prosthetic leg, he returned to his birth home and thought about the rest of his life. He decided that it would be as an agent with Z5. It was a decision his mother fought vigorously but if there was anyone alive with even more determination than Marion Palfrey, it was her son, 'Doc'.