Closer Than Enemies — L.S. Sygnet

In 1978, five children are missing. A desperate family turns to the police for help, but because it is a matter of custodial interference, it is not a kidnapping. Wendell Eriksson, along with a new unofficial partner, takes the case despite being forbidden to do so. He crosses half the country to rescue the children from a nightmare, which becomes a murder investigation along the way.