The Avengers (sometimes even in color!)

I just spent some $60 on a set of DVDs of "The Avengers," the 1960's British TV show, not the Marvel Comic. I have watched a few episodes on a smaller set of DVDs.
I had forgotten how much I like that show. I wish I had a lot to say about it, but perhaps I shall post more after I finish watching the episodes. There are 17 discs in the series, of which I already have two.
I used to like watching "The Avengers" when it was sandwiched at noon between "The Fugitive" and "Perry Mason." I can think of no better lineup of re-reuns. (There are a few that would as good, but probably none better.)
After re-watching a few episodes as I wait for the full collection, the only thing that really jumps out as noteworthy is how good the on-screen chemistry is between Diana Rigg and Patrick MacNee. It all had to do with the way the characters interacted. Macnee, as John Steed, and Rigg, as Emma Peel, were playful and clever with each other, without falling out of character.
The movie of a few years ago with Uma Thurman and Ralph Finnes, which should have been really good, stank by comparison. They are incredibly accomplished actors, but for some reason just didn't work well together in those roles.
Some people are good for some roles, I guess, and others aren't.
Anyway, I am anxiously awaiting the larger collection. I shall report more later.
One question, though: What were The Avengers avenging? I don't think the series ever told us.