Former New York detective Carrie Wells has a scarce medical condition called hyperthymesia, which makes her possess an extremely detailed autobiographical memory. She reluctantly rejoins the New York City Police Department's Queens homicide unit after her former boyfriend and partner approaching her asking for support in a murder case. The return allows her to discover the only thing she has been unable to remember - the day her sister was murdered when they were children, and embark on a quest to bring the killer to light.