You now need to track back to the warehouse, where you have recently been fighting with the heavily-armored enforcer. First of all, you need to return to the Drug Lab that you have already cleared, and go towards the Eastern door to the side corridor [Hidden Facility Maintenance]. Batman will be experiencing various hallucinations which you can entirely ignore. Reach the Elevator Access and get above on the elevator.
You need to be prepared because, after you walk into the Concealed Room Batman will be attacked by Copperhead for the first time. Eliminate the clones and remember to hold down the counter-attack key/button to avoid the enemy armed with a knife. Walk into the Warehouse where you will have to fight the abovementioned boss.