Once we have found and examined all six victims, we’ll be given an updated objective to find and apprehend the killer. Fortunately, the game will also place an objective marker on the map showing you exactly where to go - the ‘Pretty Dolls Parlor’ in western Founders’ Island.
After arriving at the location, enter the building and proceed through the next door until you reach the weak wall. Use Explosive Gel on the weak wall here to bring it down.
Move down the hallway and you’ll reach a circular walkway with a surgical theatre of sorts in the centre. Make your way down into this area and enter the central room for a scene.
As soon as the scene ends, hit the counter button to incapacitate the enemy. After a few moments it will rise again and you’ll need to beat him down once again. We’ll need to perform a ground takedown on it to have it stay down.
Taking the sole enemy down will have a further five drop down into the operating theatre with you. You’ll need to fight them all off and perform ground takedowns on each and every one of them to continue. Early on be sure to use your throws to put distance between the various enemies and try to stay out of range of melee attacks as you go in for the finishers.
Once these fellows are down, a boss fight will begin.
Boss: Professor Pyg
After the scene introducing the fight, the main target Professor Pyg will hang out by the operating table in the centre of the room. He’ll summon a group of eight Dollotron enemies to attack you whilst he hides behind the table and occasionally tosses knives at you from a distance.
To complete the fight, we need to knock down and perform ground takedowns on all eight of the minor enemies. As with before, try to use throws to get knocked over bodies away from the main bulk of enemies and perform ground takedowns when you are unlikely to cop a melee strike from other bad guys. You’ll also want to keep your eyes on the boss who will periodically throw a set of three knives in your direction.
Once all of the Dollotrons are down, it’s time to deal with the boss. Unfortunately, he will stay on the far side of the table from you and it is impossible to actually approach him. Fortunately, there is an easy way to deal with him. Wait for Professor Pyg to throw the knives at you and counter all three of them. If done correctly, the third will be deflected back at the boss and stun him temporarily. At this point you’ll want to approach the operating table and perform an environmental takedown to finish the fight.
Following the fight, interact with the fuse box on the wall by the exit to release the other prisoners and to open the door. Pick up Professor Pyg and take him outside before placing him in the Batmobile.
Drive back to the GCPD headquarters on Bleake Island and park in the indicated spot to complete the side-mission.
Track down and apprehend the serial killer.