«NIGHT FEAR» by Paul Lawrence Samuelson

Wounded and dying, paratrooper Mig Czerniak was picked up by Army medic Eddie Fulham on a German battlefield in 1945.
The war has been over for two years, but it still rages inside Mig. Racked by nightmares of combat, periods of uncontrollable shaking, violent outbursts of anger, he's lost, barely hanging on–Then he learns that Eddie Fulham has died. Mig knows a secret about Eddie that makes him believe the late night hit-and-run was murder. He sets himself to find out who did it and why.
Mig's search brings him to the small California town of Ventura, where he fails to convince police lieutenant Nate Prye that what happened was anything more than an accident on a lonely country road. The lieutenant's concern is with the disappearance of a 12-year-old girl, Peggy Beledayne.
Prye, resentful of Mig's hammering him and against his better judgment, examines the death scene and finds evidence that makes him wonder if the bothersome ex-GI could be right.
Mig finds out that Eddie was involved trying to stop the highjacking of a shipment of morphine to troops still fighting in the Pacific after the war ended in Europe. He comes to suspect that a mayoral candidate of Ventura is behind the stolen morphine, one who's also related to the missing girl.  
Acting on his own and relentless in his pursuit, Mig walks into a killer's trap that almost destroys him before he can bring Eddie justice and put an end to hidden, shocking crimes.