Once you start the level, look to your right and go to the pill in the corner. A message will appear, stating "Silent Walk pill has been activated and all enemies deactivated!". No enemies will attack in this area now. Enter the door near the statue, but do not take any of the pills ahead. In the following area, shoot the spike in the center of the pool (without taking any pills) to find some health. Note: It is guarded by two Reptiloids.