Walkthrough - Arkham Island #4 BAA Guide

Make sure that you're still using detective mode and follow the trail by searching for yellow icons near the ground. The trail will lead you to a passageway to Arkham West which is going to be marked as the Abandoned Tunnel. Use your hook along the way in order to get past a closed gate.

Enemy units are stationed nearby and if you look closely you'll notice that two of them are carrying guns. Obviously you'll have to plan your attack by using the Glide Kick against one of the armed opponents. Once he's been hit quickly take care of his colleague. Make sure that threat has been neutralized and eliminate the rest of the goons.

You may proceed to Arkham West without any other delays. It's important to remain cautious here, because the nearest guard tower is now being occupied by an enemy sniper. CAREFULLY approach the tower from the south-east and use your hook on the structure. You can now wait for the sniper to turn around or you can throw him over a balustrade when he's near you.

You've now got two options - you can keep following the trail closely or you can proceed directly to the Penitentiary. You can locate this building easily, because the main entrance is going to be heavily guarded. Attack the inmates. Be careful, because one of them will be carrying a stun gun. Once you've won talk to one of the civilians and proceed to the large door. You'll find yourself in an area called Cells Access.