Alister Woodhead is an agent for the Ministry of Scientific Research.
In that role he is responsible for helping make sure the secret work done by the various high security laboratories remain secret, a job normally of a preventative than reactionary nature. For Woodhead, though it is often the latter as he is the one called with the door is found left open, not the one seeing the door is normally closed.
Prior to the series, Woodhead had, apparently, a very interesting and well traveled youth having lived for a time in Manchuria and other exotic areas of the Far East. Then came university and a degree and love.
When the series begins, Woodhead was a newlywed, just married to the young and lovely Elizabeth and building their home in Surrey. The War intrudes and Woodhead is called for duty. His experience and his training sees him assigned to a highly secret detachment responsible for fighting the enemies who made it to England. Numerous adventures occur during this service, only two of which are recorded, resulting in Woodhead reaching the rank of Squadron-Leader with more than his share of medals and commendations.
After the war, able to return to his home again, Woodhead has to look for gainful employment now that his service is over. He chooses the Ministry where he is promised a quiet time devoid of the action and danger he had seen in the War. He gets the job but doesn't get the quiet.
As time goes along, Woodhead and his family age naturally and in an entertainly manner. Most importantly to this aging process is the way that Woodhead becomes a fair degree of a curmudgeon, annoyed with any job that takes him out of the country and not too happy with any that keep him in the country. He has a fair number of mannerisms which make him entertaining, not the least of which is his basic desire to not have much to do with other people. He isn't anti-social so much as just not that friendly. Deliciously so.