Driving home one rainy night, Cassie Larkin sees a man and woman fighting on the side of the road. After calling 911, the veterinarian makes a split-second decision that will throw her sedate suburban life into chaos. Against all reason and advice, she gets out of her minivan and chases after the violent man, trying to help his victim. When Cassie physically tries to stop him, he suddenly turns on her and spits out an ominous threat: “Let her die, and I’ll let you live. And this will change her life.”