Leo Kasper is a playable character in flashback levels and a bonus episode.
A psychopath who was also put in the asylum by the Project. He was once a government agent and has expertise in combat, evasion, infiltration and assassination techniques. He helps Daniel Lamb escape and teaches him his own well-honed tricks of the trade. At first Leo appears to be a real person but in reality he is a personality created by the Project and implanted into Danny while remaining separated from Danny's own mind by the Pickman Bridge. However, the Pickman Bridge was not perfected yet and it resulted in Leo being able to freely talk to Danny inside Danny's head. His personality also took over at times when it was not called upon. More than anything, Leo wants the Pickman Bridge removed so he can take over Danny's mind and body forever. Leo helps Daniel a long way, but with the ultimate goal of trying to get Daniel's body, even going so far as to murder Daniel's wife to sever another tie to his past. In one ending, Leo confronts Daniel in his mind. If the player plays as Leo, Leo fights Daniel and wounds him with a gun. Cursing the Project and those involved in it, Leo steps on Daniel's neck, killing him. Leo shouts aloud that he won and is then awakened by Dr. Laura Whyte in Daniel's body, she explains she removed the Pickman Bridge, thinking he is Daniel. Leo tells her to gather the staff to resume work on the project.