In 2039, that era's Batman has a completely new Rogues' Gallery that is a far cry from the original Batman's merry, but often mad, band of bad guys & gals. However, that all changes in the first---and so far, only---feature film spun off from Batman Beyond. Return of the Joker sees the Clown Prince of Crime (Mark Hamill) seemingly return from the dead.
In a previously untold case, Batman (Kevin Conroy) & Batgirl (Tara Strong) attempt to rescue Robin (Matthew Valencia) from Joker and his on-again, off-again squeeze, Harley Quinn (Arleen Sorkin, Days of Our Lives). However, Robin, in this case Tim Drake, has been transformed into Joker, Jr., brainwashed by the madman of mirth. The ages-old human chess game between the Batman and Joker ends with the Joker's death, but is that the end of the story? Drake was deprogrammed, and forced to retire from crimefighting.
In 2039, Drake (Dean Stockwell, ex-Quantum Leap) is married and a successful engineer, proving there is life after crimefighting. But, with the Joker's sudden reemergence in Gotham, targeting Bruce Wayne in particular, and taking over the Jokerz street gang, the current Dark Knight, Terry McGinnis (Will Friedle) questions Drake after Wayne has been attacked and injected with Joker venom (Wayne survived, of course). Drake is still bitter. With Wayne unwilling to shed light on the past, Terry turns to Commissioner Barbara Gordon (Angie Harmon, Law & Order). Gordon had ended her career as Batgirl after that fateful night, and Wayne apparently vowed never to put any more children at risk.
But as it turns out, Joker had an ace up his sleeve, implanting a microchip in Drake that enables him to transmute into a new, slimmer Joker, with the Clown Prince in control. Well, you knew there was a catch, didn't you? Before going further, here's the trailer:
Suffice to say, there is a happy ending, and that's all I'm going to disclose. I was not that big on the futuristic Batman to begin with, and the movie doesn't change my personal opinion one bit.