I still don't understand ...

professor had an affair with the sister (guest lecturer on subconscious memory), who's brother died in car accident (who's identity he assumed - the protaginist who's going crazy). the sister threatened to blackmail the professor with the pictures she took of them together in bed when he's asleep. to protect his reputation & marriage, he opted to poison her before disposing of her body via dismemberment. after the fact, professor realizes his lover was pregnant with his baby. he's driven crazy by this, and suffering from multiple-personality disorder, phases in and out of killing psychosis to eliminate all those aware of his indescretions. or something like that