No bad deed : a novel
(Book)

When veterinarian Cassie Larkin sees a man and woman fighting on the side of the road she calls 911. She then gets out of her minivan and chases after the violent man, trying to help his victim. He turns on her and spits out an ominous threat: 'Let her die, and I'll let you live' and then steals her car. Now he has her name, her address, and he knows about her children. The next day-- Halloween-- her husband disappears while trick-or-treating with their six-year-old daughter. Cassie will have to go to terrifying extremes to save her family. -- adapted from jacket