May the best liar win(the red rose killer)

The red rose serial killer has killed nine women and the police didn't have any leads until now.There is footage of a woman living one of the crime scenes;Monica Stevens. The police believe she's the killer and are hoping to make an arrest.Things seem clear until they find out she has an identical twin;Sarah.Both claim to be innocent.Will the police make an arrest before the killer strikes again or will an innocent woman pay for her sister's sins.