O nome do romance é "Sussurros", escrito em 1990 por Dean Koontz.
Wiki site aqui:
assassino em série, acaba sendo gêmeos criados por sua mãe para acreditar que ambos eram a mesma pessoa, em dois corpos.
MATCH: Katherine gave birth to identical twin boys. The twins were born with cauls on their faces, leading the mentally unstable Katherine to believe they were demons. She raised her sons as if they were one person. They were both called Bruno, and both were rewarded or punished for anything either one of them did.
Em algum lugar no final do livro, um dos gêmeos é morto,
PARTIAL MATCH (This actually occurs relatively early in the book): The next day Frye returns and attacks Hilary again, this time receiving several stab wounds before escaping. She calls the police and once again meets with Clemenza, who tells her that Frye's body has been found and takes her to the morgue to identify it.