Batman is now an old man, retired for 10 years, mourning the death of Robin. The plot is essentially a man cannot escape his destiny and a chance to conclude unfinished business. In the 1980's there are two towering graphic novels that rewrote the rules of comics in the West. One was Watchmen which a few years ago was turned into a very good (although not perfect) live action film. The Dark Knight Returns (DKR) is the other, in one epic graphic novel Batman was turned from camp, costumed, kid friendly hero into a bitter, noir, menace. Prior to DKR Adam West was the definitive onscreen Batman, after DKR we have had much more intimidating and serious versions of Batman peaking perhaps with the Dark Knight.
Therefore bringing such a key graphic novel to the small screen can lead to worry. There are two areas that bringing it down from 5 star to 4 for me. Firstly the animation while better than the average Saturday morning cartoon is still a little bland for such a distinctive looking graphic novel. Frank Miller's scratchy pen work gave the whole thing a feral look which is now gone . Secondly The inner monologue is also gone so some great lines are absent and there's more silence in this film than you'd expect. I appreciate the animation choice is probably for both technical and budgetary reasons. Similarly Seeing a moving image version means you see just how bleak and sinister some of the scenes are and if a growling voice over had been added it may well have made the whole thing feel positively nihilistic. It shouldn't have been all thrown out, but I can understand why it wasn't added.
So with those two exceptions you have a very loyal animated version of one of the greatest graphic novels ever made. This is thoughtful, classy, grown up stuff and thoroughly recommended to both batfans and lovers of a good noir story. I lent it to my brother-in-law who had never read DKR. He texted me a one word summary "impressive".