At one point in the game, you will encounter a police officer who will ask you to free him. He will also tell you not to turn the three valves in front of you or he will die. If you want to save him, you must first have a full insanity bar. You can get to that state by going back to the previous room and killing the respawning enemies.
Once you have a full insanity bar, open the door and go into the room with the three lockers on the wall. Go into the room after that. Look around you should see a broken wall. Transform into your insane form and carefully destroy the broken wall, making sure you do not kill the police officer. Transform back, and when the police officer runs out and sits down, your good deed will be done. To progress into the level, turn the three valves and stand back. When they explode the previously inaccessible room to the left of the valves will now be open.