 Flanagan observes that in Tenebrae , Argento offers two characters who suffer from impaired vision . Gianni ( Christian Borromeo ) is an eyewitness to an axe @-@ murder , but the trauma of seeing the killing causes him to disregard a vital clue . Returning to the scene of the crime , he suddenly remembers everything , and is murdered before being able to tell anyone . Homicide detective Giermani reveals that he is a big fan of the novels of Agatha Christie , Mickey Spillane , Rex Stout , and Ed McBain , but admits that he has never been able to guess the identity of the killer in any of the books . He is similarly unable to solve the real mystery until the last corpses are piled at his feet – he cannot see Peter Neal for what he really is . 
