The Prisoner lasted just 1 season, but it was enough to merit it cult status.
There are those who dispute the idea that Prisoner was created as a follow-up to Patrick McGoohan's previous series, Danger Man (known as Secret Agent in the US), a collaborative effort between the star and writer George Markstein. Markstein, it seems, intended for the title character, code-named Number 6, to be, in fact, John Drake, but that's been debated for nearly 50 years, and nothing since, not even a comic book adaptation by Dean Motter for DC, or a miniseries produced 5 years ago for A & E and starring Jim Caviezel (currently on Person of Interest), has resolved the issue.
This much we know. A retired secret agent (McGoohan) has left his agency and is preparing for vacation, unaware that he's been followed. Knockout gas is pumped into his apartment, and he wakes up in someplace known simply as "The Village". Escape is nigh impossible, thanks to a balloon-like entity, Rover, who either recaptures or kills escapees. George Orwell would've loved this.
Here's the intro: