If you’re a fan of a quick, tightly knit plot involving secret agents, you may want to look up an old series that has favorably impressed us called Danger Man (aka Secret Agent). Made starting in 1960, each episode (at least in the first season) is a half hour long, B&W, and follows the adventures of John Drake, American secret agent, as he foils plots against the Western world.
This is not a pain-free series. Drake loses friends to temptation and to death, he has to make hard choices, and explores some of the backwaters of morality, all in half hour chunks. Episodes are not connected, so it’s easy to watch them at convenience.
