After suffering through the Gunfight at the OK Corral, the TARDIS materializes on a futuristic planet. The Doctor, Steven and Dodo are quite unexpectedly expected by the civilization of the Elders, who have been tracking the ship through space and time. The Doctor, for one, is delighted by the warm reception from an advanced and enlightened civilization. Delighted, that is, until he learns the secret of their post-scarcity society.
Much Science Fiction takes the optimistic, Star Trek approach to a post-scarcity economy. In this setting, it is technology that has somehow solved the problem of want, leading to a truly just and equitable society. In the aforementioned space opera, "replicators" literally materialize food and materials from thin air without resource extraction or manufacturing industry.
Yet in real history, those societies that have come closest to any kind of post-scarcity economy have actually built luxury on top a foundation of oppression. Though we might laud ancient philosophers like Aristotle and Aurelius for their enlightened insights, the only way for a person thousands of years ago to have enough time to sit and think was to own slaves who did the actual work. In relation to the Ood, the Tenth Doctor made this same observation about modern Western civilization and its reliance on cheap wares produced by Asian sweatshops (for example, the First Doctor and TARDIS playset sitting on my bookshelf, and my bookshelf itself).
The Savages makes a very transparent analogy for this. The Elders' society is made possible by literally sucking the life-force out of another race, called the Savages. The Savages were themselves once a proud and creative race whose culture and ambition have been robbed of them by the life-sucking machinery of the Elders. The Doctor cannot condone this exploitation, so his punishment for speaking up as an activist is to be subjected to the machine himself. Meanwhile Steven and Dodo integrate into the Savages and ferment revolution in what essentially amounts to a terrorist cell. Sometimes Doctor Who can be just as timely as when it was written.
Unfortunately The Savages is also one of the serials lost to posterity by the BBC's shortsighted policy of disposing tape in the Sixties and Seventies. All four episodes of the serial are lost, save for a few brief snippets to be seen on the Lost in Time DVD set. The soundtracks remain, narrated for CD by Peter Purves. Besides the misfortune of missing any of the series, this is especially disappointing because we lose the departure of Steven Taylor, as played by Peter Purves.
At the end, the horrible life-sucking machines have been destroyed and everything is back at square one. That includes recrimination and suspicion. Just as in 1927's Metropolis, there must be a mediator between the head and the hands. That is the heart, and in this case, the impartial mediator is Steven. Encouraged by the Doctor, he gives up a life of roaming to settle into life brokering peace to a world in need.