Shift, also called stealth by gamers, is a skill that can be utilized by Hayden in combat. By holding "Y" (XBOX 360), Triangle (PS3), or E Key (PC), Hayden becomes invisible to all enemies and even cameras. Using this allows one to move to a more advantageous position or to execute automatic Finishers against most enemies. It is unlocked by defeating Stalker during the game.
Shift is the only way to get the Ghost Achievement.