A lot of us depending on our placement in life always have a fantasy that we could somehow be involved in some sort of important dangerous work like espionage in order to make everyday life seem like another day. Bascally the story is simple, Amanda King (Charlie's Angels, Kate Jackson) is your typical everyday woman, she's a housewife recently divorced and is taking care of her kid own her own; she doesn't really mind living her everyday existence (but on the inside you can tell she's bored and a bit lonely) and wasn't looking for trouble. But fate steps in when a super spy during a situation he is escaping from in a hurry he bumps into Amanda and gives her a package to protect. She for some reason believes him and complies. And of course the super spy is Lee Stetson Alias Scarecrow (Tron/Babylon 5, Bruce Boxlightner) he works for "The Agency" a branch in government intelligence and defense. Due to Amanda's involvement with Lee's assignment both of them are partnered up and have to work together (whether they like it or not) defending America from evil.
That's all there is to it, story's format is slightly similar to Hichcock's "North by Northwest" or "True Lies" both which take normal people into rather unbelievable and dangerous circumstances. Never mind most of the plot lines in the show which were a little ridiculous or by todays standards rather dated. As the Hichcock films put it, the plots were really just a Maguffin device. Or even a few inconsistencies, one big inconsistency is Mrs. King who despite working for The Agency gets no special training of any kind (wouldn't a government agency be concerned about giving her the essentials to go on dangerous missions?). What really counted and made the show good was the chemistry between the two characters which was funny and romantic.
The duo is like a lot of romantic duos with developing romances in plenty of shows you may know (Moonlighting, Lois and Clark, Inuasha). However what made this two click was that you actually felt they were one step in reality which actually made you appreciate and care for the two. Both of them are characters we actually get to know and find lovable; Lee is a determined tough as nails American James Bond who always gets the job done by any means necessary and wants his life to be anything but normal (although you sense at times he want to take a break once in a while). Amanda is a reluctant hero but always does the right thing at the right time, has a bit of bad timing which works to her advantage, funny, sweet, intelligent, has a husky vocal charm and wit and despite no special training she always got the mission completely by doing simply whatever she can logically do in the situation. Both give each other grief, never fully accepting each other world, liking or disliking one another, both save one another from trouble or get into trouble, but their relationship developed like any other they started out as partners, friends, then lovers. The writers really timed the development right just making it slowly but surely develop and knowing the proper places where it lead to. It's true that by Season 4 even though it wasn't bad you did sense that the show was starting to lose steam mainly due to things beginning to feel a little routine. But the chemistry was never lost and in the end about on the final episode it lead to the two getting married but of course both of them had to keep it secret for protection which made dramatic sense. The show ended at the right time and alright (at least for some). Scarecrow and Miss King are a very unlikely couple but they have one thing in common they love trouble and each other.