 McDonagh noted that two sexually charged flashbacks are key to understanding Tenebrae. These distinct but strongly related memory fragments are introduced repeatedly throughout the film, usually immediately following a murder sequence. Although the flashbacks are never fully explained, the first reveals a beautiful young woman's sexual humiliation (though oral rape) of a teenage boy, presumed to be Peter Neal. The young woman is mostly topless during this first sequence, and she humiliates the young man by jamming the heel of one of her shiny red shoes into his mouth while he is held down by a group of gleeful boys on a pale-white beach. The second flashback shows the vicious revenge-murder of the woman some time later. McDonagh notes that all of the fetishistic imagery of these flashbacks, combined with the sadistic details of the murder sequences in the main narrative, "set the parameters of Tenebrae's fetishistic and fetishicized visual vocabulary, couched in terms both ritualistic and orgiastically out of control ... Peter Neal indulges in sins of the flesh and Tenebrae revels in them, inviting the spectator to join in; in fact, it dares the viewer not to do so."
