For advanced gamers only. This effect applied to the special infected makes them invisible, although good players will hear them before anyone could see them. Use your flashlight to see their outline and shadow.

Is Left 4 Dead not scary enough anymore? Maybe you never thought it was? The Poltergeist special infected will scare the ♥♥♥♥ out of you. You can spot them with your flashlight, their shadow, or the sounds they make. Some of them, like the Smoker or Spitter, will leave glowing trails of smoke or blood behind them.

Choose a flashlight, or if you are in the mood for a scare subscribe to Survival Horror Mode, a no-flashlight mod.