Who is the antagonist in the novel, Mistress?

The novel is filled with characters that can be defined as antagonist, but the antagonist that initially drives the plot forward is Detective Liz Larkin. She is the officer who officially arrests Ben after Ellis is killed, even though she does not yet have specific charges. Ben tells Larkin his story but she doesn’t believe him. Instead, she uses information she has dug up on his mother’s death to create a pattern between Ben’s mother’s murder and Liu’s murder. It is also Larkin who suggests to Ben that reciting presidential trivia is an attempt to bond with his father.