The other reviewers have given a good "recipe" of the plot so I won't do the same. Hannah Swenson can be entertaining and I've copied down some good recipes. But for someone who is supposed to be smart, Hannah Swenson can be incredibly stupid. She locates the murder weapon, a tire iron, is left alone with it for an apparently lengthy period of time while waiting for the murderer to return (knowing he's the murderer), but instead of putting it in her vehicle and taking off, she tries to buy it from the murderer. When the murderer realizes he's been outed, she runs off into the salvage yard with--not her car keys--but a bag of cupcakes.
Then, while hiding in a junk car, listening for the sound of footsteps on gravel to indicate the approach of the murderer, she somehow misses the sound of heavy equipment approaching. It's ridiculous that someone can miss the sound of car moving equipment and then be completely stunned when the car mover scoops up the car in which she's hiding. Had she stumbled across a tree root, it would have been a perfect rendition of the incredibly dumb girl in horror movies that everyone in the audience yells at not to be so dumb.
Then, when Mike the handsome cop arrives and stands immediately below her elevated hiding place, he somehow misses the leather jacket that floats down from above (which Hannah tossed down to get his attention), gets hit in the head with a fudge cupcake but doesn't look up and only becomes suspicious that something is afoot when he gets bonked with a second cupcake. Honestly! How dumb and blind can one supposedly brilliant cop be?
And Hannah's approach to romance needs serious work. She's blindly attracted to Mike for his looks and sex appeal, even though he treats her like a silly girl, cautioning her in a clearly paternalistic and condescending manner (more than once) to "let the professionals handle it," the murder investigation, which he has done in each and every book. The only thing missing was a pat on the head. A dozen pages later, Hannah's mooning about, wondering if Mike will propose, despite the fact that she knows he's condescending, knows he's still mourning his deceased wife, knows he's not interested in commitment.
Hannah is supposed to be level-headed, no-nonsense and bright. What she apparently really embodies are all the old cliches about women--willing to overlook the handsome man's personality flaws, dreaming about proposals of marriage, getting into tight corners (in this case, a junk car about to be squashed to bits in a junk yard car crusher) because she just doesn't think logically and relying upon the big strong men in her life to rescue her. It would be different if Hannah recognized the dichotomies of her life; at least there would some depth there, but she doesn't. The characters in this series simply are not progressing.