Martin goes to visit the painter a couple of days later and finds out that he had died.  He gains entry to his apartment where he sees dozens of paintings similar to the one he has.  Cécilia that he saw with the Meyers that night comes in, and he finds out that most of the paintings are of her, and that Meyers died while he and Cécilia were having sex.

Martin begins an obsessive affair with Cécilia.  Which quickly descends into a sadomasochistic relationship, due to Cécilia's inability to take anything into consideration other than what is happening at that moment in her life and Martins' total failure to understand this.  After the relationship degrades even further into complete loss of self-respect and jealousy, Martin crashes his car and when he awakens seems ready to begin a new, less destructive lifestyle. 

Cécilia certainly is not a good promoter of men not treating women as sex objects.  But that may be the point.  Cécilia fucks Martin and leaves, never has a conversation with him, and never shows any interest in developing their relationship into more than what it is, sex.  She treats Martin purely as a sex object, even continuing to see him after he discovers she is sleeping with an actor friend of hers.  Maybe he thought he wanted an uncomplicated affair with just sex and nothing more.  But now that someone is participating in that with him he does not like, nor understand how Cécilia can be so detached from him, and any feelings she may have for him.

He continues the relationship with Cécilia, begging her to stay with him.  Degrading the whole relationship into loss of self-respect jealousy and masochism.  Though Cécilia is not intentionally sadistic, sadistic is still what she is.  She is obviously aware that she is causing Martin pain, but still does not do anything to change the way she is.  And is not a person who does not take into consideration anything other than their pleasure or their immediate circumstances, with no regard whatsoever for anyone else, indirectly a sadist anyway for the pain they cause to those around them?

But is Martin's pain, pain at all?  Is it not maybe just that his failure to understand and change the way Cécilia acts, his complete inability to control and possess her?   Or does Cécilia secretly glean pleasure from the pain that she is causing?  But does not understand that that is what she is feeling, or maybe does not even think about it, all she knows is she feels pleasure, without thinking about anything how could she know that this does not come from sadism?  As Cécilia is so emotionless in everything she does it is difficult to fathom.