After leaving the Medical Center in the church and going to GCPD, you will lose contact with the Medical Team. Head back to the church to see whats going on.

When you enter the church, there will be no sign of the medics. Instead, you will see the Riddler on the screen above. He will tell you he took the medical team hostage, and that you need to answer his riddles if you want to save them. He will give you several conundrums to answer.

Riddle #1:
I am an instrument whose music always comes from the heart. What am I?

Solution:
Organ.  Find the Organ on the far edge of the church.

Your objective now is to rescue the hostage from the courthouse. Download known riddler associates to your batcomputer. When you go outside, there will be a party of thugs waiting for you. Take out all thugs EXCEPT Riddler informant to interrogate him. The Ridder Informants are glowing green. Dont attack them, instead just COUNTER their attacks while you defeat all other thugs in the area. Make sure NOT to hurt the Riddler informant.

Once you have taken down all other thugs, you will now be able to interrogate Riddler's informant. Riddler secrets will now get added to your map: Church/Medical Center, Park Row.

Continue to the Courthouse. Beat the thugs guarding the entrance. Again, there will be a Riddler Informant (green) amongst them, make sure to keep him alive and interrogate him for more secrets. Enter the courthouse. Beat the thugs inside and rescue M.P.T. Eddie Burlow. He will tell you some numbers: 2-7-5 3-2-5. That is a radio frequency. Use your cryptographic sequencer to decode the broadcast. The MPT will also give you an Enigma machine. Use the Enigma machine to solve the riddle and locate the next hostage.

Bang! Bang! Order in the court
Riddle #2:
If you know me, you'll want to share me but if you share me, I'll be gone. What am I?

Answer:
Secret. Rotate the left wheel to have "SEC" on the right. Rotate right wheel to have "RET" on the left. This will form the word "SECRET".

FIRST RIDDLER HIDEOUT

You need to have found a certain number of secrets to gain access to the next riddles. If you dont have enough, Riddler will tell you its too soon, and you will be instruccted to find more Riddler secrets to reveal the location of the next riddler room.

The next hostage will be in the First Riddler Room. Head south of the church. Find a wall with green painted question mark on it and smash it. Enter the building. Go through the doors with the green question marks on them. Locate the hostage room. Medic Adam Hamasaki is tied up on a platform above. You have to navigate through electrified squares on the floor. Use Batarang to hit question marks on the far walls to de-electrify the next squares and keep hopping through the safe spots. Reach the elevator and use the Batarang to press the remaining switches so that it rises, the glide down from the elevator and rescue the hostage.

He will give you the next frequency: 6-2-5 9-2-5. Use this to get the next riddle.

Riddle #3
The more there is, the less you see. What could I be?

Solution:
Darkness. Rotate the Left wheel to "DARK" and the right wheel to "NESS"

SECOND RIDDLER HIDEOUT
Secrets Needed: 80

Your objective now is to rescue the hostage from the second riddler room. The 2nd hideout is located South East of the church. Go there. Break through the wall with the green question mark painted on it. Go through the door. You will come upon a room where the M.P.T. William North is sitting tied up on the other side. He will be "shuffled" into one of three cages. Enter Detective mode to see where he is  and Batarang the question mark  under the cage where he is held (in our case it was the leftmost question mark)

Jump to him and release him. He gives you the next frequency code. 8-6-0 1-2-0. Use it to get the next riddle

Riddle #4
I have a head, a tail, but never any legs. Do you know what I am?

Solution:
The answer is "Penny". Set the left wheel to "PEN" and the right wheel to "NY"

THIRD RIDDLER HIDEOUT
Secrets Needed: 160

Your objective now is to rescue the hostage from the third riddler room. He is located in the industrial district, on the eastern edge of the city. Make sure you have already picked up the Line Launcher before going there. You will need it.

As usual, blast the wall with the painted question mark. Open the door.  You will enter a room with some big drills. You will hear the doctor crying for help.

Select the Freeze Blast and throw it into the water. The water will freeze. Use line launcher or batclaw to cross the water and grapple to the platform. Shoot the REC electric gun  on the upper electromagnet to the left of Riddler's screen. This will move a generator to the left. Use your remote control batarang to hit the question mark underneath it. Then hit the magnet on the right do the same for the right question mark. This will open the round gate. Use your line launcher to navigate through the deadly rotating blades and enter the passage to the right.

Observe the three industrial electromagnets in this next room. Fire your REC gun on the high electromagnet to bring the box to it, then on the low electromagnet to your left to get the box to the floor. Use REC on magnet to repulse the box towards the electromagnet in the center. When it crosses the center, repulse it towards the pressure plate. This will disarm the security door and you can now free the hostage. She will give you the next frequency: 6-0-6 1-2-0

Riddle #5
I'll be right under your feet, in the midday sun. You cannot lose me, no matter how you run. What am I?

Solution:
Shadow. Set the Left wheel of the enigma machine to "SHA" and the right wheel to "DOW".

FOURTH RIDDLER HIDEOUT
Secrets needed: 240

Head towards the fourth riddler room, to the SW of the industrial district. Break the wall with the question mark and enter the building.

Go through a couple of doors. In a big room, a hostage is hanging from the ceiling, beneath him the floor is electrocuted. There is a broken bridge in the middle of the room. A big blade moves through the chamber.

Use cryptographic sequencer to hack the console near the door. A walkway will emerge. Observer the blade, and run on the walkway when it is safe to do so. Reach the last square, the one that has a question mark on it. You should now be in the right angle to be able to shoot your batarang at the question mark on the top of the bridge on the far side of the room. This will turn off the electricity on the squares leading there. Go there and jump onto the section where the question mark was.

Climb onto the bridge and run towards the other side, jumping through the gap in the bridge. Duck whenever the blade approaches. Use line launcher to get to a room in the side of the wall. Use explosive gel to blow up the weakened wall (the one where the image of Riddler appears). Use REC gun on electromagnet to move box away from the question mark and give room for your Remote Controlled Batarang to  go under the fence hit the switch. This will disable the force field. Go through the disabled force field, step on the green question mark, and double line launch to rescue the hostage. He will give you the next frequency, 1-1-5 7-8-0

Riddle #6
Hit me hard and I will crack. But you'll never stop me from staring back. What am I?

Solution:
Mirror. Left Wheel: "MIR". Right Wheel: "ROR"

Fifth Riddler Hideout
Secrets needed: 320

Your objective now is to rescue the hostages from the final riddler room. The final hideout is found to the NorthEast of the church, in the Amusement Mile. Head there and break through the wall with the green question mark.

Find M.P.T. Anne Bishop trapped on a platform inside. Slide underneath the gate. Use your REC electrical gun on electromagnet to the top. This will lift an obstacle, run fast sliding under two more gates.

Step onto the red squares. From there, aim and throw your batarang on the question marks that get lit. Do it fast and you will disable the electricity in front of you. Head towards the green question mark on the wall. There will be a force field in the hallway in front of you. Use remote controlled batarang twice to hit the two green question mark switches on the other side of the hallway. Jump across the pit. Climb the ladder. Do a double line launch through the circular blade gate and hack the console. Head back  using line launcher, go to security field that was disabled. Grapnel across the room to the top. Use the magnets to Repulse boxes out of the way. Now use a TRIPLE line launch sliding above the electrified panels, turning two corners, and when you are in the area with the opening in front of the platform where the hostage in, line launch onto her and rescue her.

There are still more hostages. You will ask the hostage for the code, but the Riddler didnt give her any because he did not think you would beat this challenge. Contact Oracle telling here you solved the last Riddler room but there wasn't a radio frequency.

FINAL RIDDLER HIDEOUT!
Secrets needed: 400

When you've found 400 riddler secrets, Oracle contacts you that she has found something linking the riddler rooms. The location of Riddler's hideout will now show up on your map. Location will be in the Bowery area, in the southwestern part of the city.

Your objective now is to find Riddler's hideout and take down the riddler. Once you get there, fly and glide under some tunnels and over an electrical fence. Enter through the door. There is another door but it is strapped with dynamite so you have to find another way.

Grapnel up, and go through a grate. Crawl down the vent.

The hostages have bombs on them and the Riddler has a remote detonator.

Ridder has attached explosives to the hostages. If they stop moving, they will die. You cannot get in their way. Observe their patrol patterns and match it so that you dont interrupt them and they dont have to stop. Work your way towards the section beneath Riddler's control room. Then use a takedown to knock him out.

Congratulations! You will get the achievement, Genius

Riddler Neutralized - Case File Closed.