The Long Kiss Goodnight

Schoolteacher and single mother Samantha Caine lives an average suburban life, until she begins having strange memories of unexplained violence and discovers that she has physical skills that she never imagined. Hiring private detective Mitch Hennessey to probe into her past, Samantha discovers that she's a well-trained government assassin who went missing after suffering a bout of amnesia and that her former handlers want her back in their employ.

R, for a substantial amount of strong bloody violence, and for strong language