Doubleback by Libby Fischer Hellmann

Little Molly Messenger is kidnapped on a sunny June morning. Three days later she's returned, apparently unharmed.
Molly's mother, Chris, is so grateful to have her daughter back that she's willing to overlook the odd circumstances.

A few days later, the brakes go out on Chris's car.An accident? Maybe. Except that it turns out that Chris, the IT manager at a large Chicago bank, may have misappropriated three million dollars.

Molly's father hires Private Investigator Georgia Davis to follow the money and investigate Chris's death. Doubleback unites PI Georgia Davis with filmmaker Ellie Foreman. The women go to great lengths to find the truth, tracking leads from Northern Wisconsin to an Arizona border town.

But when illegal immigrants, smuggled drugs, and an independent security company put Georgia's life in danger, she discovers that you can cross a line, but sometimes you have to double back.