Details of the episode are vague, other than it's all about Dick returning to Gotham at the behest of a crippled Jason Todd. Jason begs his predecessor to stop Batman from the rampage he's going on, taking out Gotham's villains one-by-one, with extreme prejudice. One shot in the trailer is sure to get Batman fans buzzing: it looks like Titans might see Batman actually take that dark plunge and kill his nemesis The Joker!
In the scene above, The Joker seems to have been thrown or dropped from a building, landing on a car and having his skull pop like a squeezed grape.
Taken with some other details of the trailer, it seems like this could all be a dark twist on the classic "Death in the Family" storyline from the comics. That storyline gave fans the option to vote on the fate of Robin II, Jason Todd, who had grown unpopular. They chose to have The Joker beat Jason to death with a crowbar, which tested Batman's commitment to his "No Kill Rule" more than any other event in The Dark Knight's career. Ultimately Batman doesn't kill Joker, and Jason is resurrected to become the infamous Red Hood. Titans seems to be spinning that mythos around, with Jason possibly having survived The Joker's assault (despite being crippled), and Batman reacting to the event by finally deciding there must be a more permanent cure to Gotham's crime plague.
...Unless the joke is on us?
This Titans finale is teasing one of the more controversial depictions of Batman that we've ever seen - one who flies in the face of just about everything know and expect from the Caped Crusader. This serial killer version of Batman could be a red herring, with Bruce Wayne having been drugged or gassed into a rampage - or all of this being a projection from Raven's father, the demon Trigun, to test the darkness inside of Dick Grayson.
Other (more far out) possibilities are someone like The Joker is pulling the strings, having faked his death in order to move freely from the shadows, driving Gotham into the type of frenzy we see Dick returning to. Scarecrow or Mad Hatter have equal potential as surprise villains that have the ability to mess with Batman's mindstate, so what we're seeing may not be exactly what we're getting.
Whatever the case turns out to be, this is all setting the stage for Dick Grayson to have to adopt a new crime-fighting identity outside the shadow of Batman's cape - one that leads right to the debut of Nightwing!
Catch Titans' "Robin vs. Batman" season 1 finale next Friday, streaming on DC Universe.