The Long Kiss Goodnight (1996)

Samantha Caine is a small-town schoolteacher and mom with no memory of her life before washing up on a beach eight years ago. After a car accident and a violent home invasion trigger flashes of her past, she discovers she used to be a deadly CIA assassin. Teaming up with a wisecracking private investigator, Mitch, she uncovers a secret government plot to stage a terrorist attack in Niagara Falls. When her daughter is kidnapped, Samantha must return to her old ways to stop the attack, rescue her child, and take down the people who tried to erase her.