After wrapping up the arc with Vandal Savage at the end of Season 1, the series skips ahead 5 years. Zatanna and Rocket have joined the Justice League, and Robin (now Nightwing), Miss Martian, and Superboy are mentoring the new team--which consists of the new Robin (Tim Drake; apparently they're skipping Jason Todd), Batgirl, Wonder Girl, Blue Beetle, Lagoon Boy, Bumblebee, Beast Boy, and some guy named 'Mal Duncan' who I don't recognize. Apparently the whole season (subtitled "Invasion") is about, as you'd expect, an alien invasion of Earth. Right now the threat are these little goblin-like aliens called 'Kroloteans,' but the real invasion is probably gonna be a heavy-hitter like Brainiac or Darkseid.
I'm legitimately disappointed that they skipped so much time, missing out on an awful lot of stuff, including what happened to Vandal Savage and the Light. But the new season does have potential.