Drive or glide all the way back to the orphanage and head inside, only to be presented with a riddle before you can join up with Selina. There are three question marks on the gate in front of you, with the periods underneath them acting as switches that you can hit with your Batarang. On the floor below you is a turning puzzle, with each switch turning one of the rings. What you need to do is hit the switches to turn the rings so the lines produce a question mark, with the arc on the top.
However, this is not yet done, as the gate doesn't open. If you position yourself just below the question mark, you should see a green light come into view. Once it's there, hold up on the directional pad to scan it, which will solve the riddle and open the gate. Drop down and head through the green door. Go to the right as Batman and stand on the switch on the ground, then change to Catwoman and do the same to the one on the left. This causes a cage to come down, trapping you both until you solve the riddle.
On either side, there will be five buttons you can hit, but they need to be hit in a certain order. If you look above them, you should see numbers flash by, which is the order that you need to hit the buttons. The only catch is that they are for the other character (Catwoman's combination is on Batman's side). The combination for Catwoman is 13524 and Batman's is 31452. Hit the switches in that order and the cage will come down...to reveal more of Riddler's robots. Defeat them all and grab the key from the glass case to finish the third riddle.
