Nightwing, Robin and Beast Boy were focused on the Krolotean data. Nightwing was explaining something when the Computer goes off:

"Unknown energy impulse detected."

A sudden ball of lightning followed by a machine appears in the room. Two figures exit the machine and—

"Tada!" Bart strikes a pose as he reveals himself while you just climb out. An alarm starts blaring as Nightwing puts the cave on lockdown. Things go downhill when Bart rambles before speeding away. You try calling out for him to wait but he's too far with Robin and Beast Boy on his tail.