The white ghost - James R. Benn

1943: In the midst of brutal conflict between the Allied and Japanese forces, Lieutenant Billy Boyle receives an odd assignment, sent by the powerful Kennedy family to investigate a murder in which PT skipper (and future president) Jack Kennedy has been implicated. The victim is an allied intelligence operative, whom Kennedy discovered on the island of Tulagi with his head bashed in. The first murder is followed by two more. To find the killer, Billy must sort through a tangled web of motives and identities, even as combat rages all around him.