Once again you need to walk along the path, lighting it up as you go, until you reach the locked door.  Unfortunately, some green monsters happen to be out for a stroll today.

The polite thing to do would be to wait for the monsters to finish, but that could take a while.

The less polite option is to shoot them.  You can’t kill these monsters, but you can stun them for a moment, so any monster that comes up behind will have to change direction.  If you can make all of the monsters walk around the path anti-clockwise, then you can walk along with them and reach the locked door.

There’s no reliable way of making the monsters do what you want, but an approach that usually does the trick is to pick a monster that’s already walking anti-clockwise, and shoot it repeatedly to hold it still.  The other two monsters will be forced to change direction, and if you time things right (and have a bit of luck) you can get all three heading the same way.