Build a platform (with hazard suit for Robin) using bricks near the entrance. Now move right, jump Robin into the water and pull the lever on the left.
In this way you will unlock electricity suit for Batman (you can move on the electrifying surfaces in it). Pass through the electrifying platform and use your suit on the receptacle (picture). Back to Robin, move right and destroy chains near platforms (they will swim out). Use them to get on the other bank of the water and use next electric machine.
Back to Robin and start heading right. After a while you will get to the fan. Destroy it and move to the corridor behind it (picture). Move right and pull the lever. Back to Batman and use another console and after that get Robin to the metal cage. Turn it using windlass built earlier by Batman.
When Robin gets to the top use his hazard suit to fill the vessel standing in front of you (picture). In this way you will lower the stairs on the left. Use them to get on the higher floor. Pull the lever on the platform (it will freeze the wall, use it to climb higher).
Move to the room on the right and destroy two valves (water starts pour out). Move to the right, destroy items near the boxes and use bricks to build platform with ice suit. Wear it and freeze the water (picture) and the wall on the background. Climb higher and jump on the other edge using freeze water from hydrants.
Use Robin to pass through ice stream from the pipe and push the windlass (you have to push the green brick). Move to the ice chamber and eliminate all enemies. After that use Batman's electricity suit to climb on top of the left ladder and use him on the receptacle (picture). Now reach the top with Robin and move him to the right using the ice wall.
Jump to the small room under you, pull the lever and push the green brick which will shows in the center of the room. Freeze the water with Robin and move Batman on the other side and activate next machine. After that get into the elevator with both heroes (picture).
In new location move to the right and eliminate enemies. Use bricks to build platform on the centre of the room and use Batman to pull the lever on the left side of the screens. Then wear Robin in acrobatic suit, make trackball and move on the platform (picture). Now you have to control the valve spot from right bottom corner to the left bottom corner.
When the container shows up fire the hook on the front side (picture). Eliminate enemies and use bricks to create platform with suit with sensors. Activate invisibility and move to the left. Pass through cameras, pull the lever, extinguish fire with Robin and move forward.
Continue march and eliminate all enemies en route. After a while you will reach the big area. Eliminate enemies, get to the green wall and use Batman's suit to scan it. Now you have to link all red mechanisms (picture). Pass through the bridge which will show on the right.
Use Robin to Freeze water on the right side (picture). Climb up on the ice wall and pull the lever which will slide out another bridge.
Pass through it and eliminate another group of enemies. Now move Batman to the high wall on the left side and scan the left top corner (picture). Press H and the battery will fall down. Now you have to set next mechanisms until battery will get to the right bottom corner.
Get upstairs and pass through the corridor with lots of enemies. When you get to the gas trap pull the lever on the left, change hero and do it the same with the lever on the right side (picture).
Move to the next location where you will have to face with Scarecrow. He will throw tanks filled with gas. Time and time again you must eliminate all enemies which will attack you (picture).
When you get rid of the smaller enemies the Scarecrow will attack you. Punch him a couple of times (picture). When he gets back to his safe position wait until he throws next gas tank and eliminate another group of opponents. Repeat it until you seriously hurt Scarecrow.
At the end of the fight you will have to use bricks to create levers on the left and right side of the chamber. Use them and the second hero will be able to jump on the platform, move him to the top and pull the lever (picture) which will activate ventilation. Repeat this with the second lever and finish off the Scarecrow in melee combat.