Question: Can someone please help? When the killer shows up at Rhyme's place at the end, he explains to him why he did it and how Rhyme did him wrong, but no matter how many times I watch it, I don't understand what exactly happened and how Rhyme was to blame for it?
Question: There is a LOT of changes if you compare the film to the book, and most of them I understand, since you always have to make some changes. But why did they change such things as characters names and genders?
Answer: The film makers changed the name of Amelia Sachs because it sounded too much like 'sex'. I have not been able to discover for certain why they made Thom into a woman, but possibly this had to do with Thom's homosexuality. It could be viewed as controversial that Rhyme's nurse is a gay man, and could possibly also bring Rhyme's own sexuality into question. To make the nurse female would avoid all such issues.
Chosen answer: The killer used to be a forensic scientist for law enforcement (where or when is never stated). Rhymes testified in court that evidence had been falsified, leading to wrongful prosecutions, the killer was sent to prison for this, where "every day I was brutalised". The killer blamed Rhymes for this, so set out to prove he was better by giving him a series of clues that he (in theory) couldn't solve. It should also be pointed out that Rhymes never met the killer or knew what he looked like.