1) Rachel is celebrating her 21st birthday with friends at her home when John goes to retrieve the birthday cake from his car but does not return.
2) Richard goes to check on John and finds them both stabbed to death by an unknown assailant.
3) The assailant is later revealed to be Ben, an ex-boyfriend of Rachel's who holds a grudge against her. He proceeds to kill Rachel's other friends one by one until she is able to fatally stab him in self-defense.