Secret honor / Book 3.
(Book)

In Wolf's Lair, a German general works toward the assassination of Adolf Hitler. In Buenos Aires, the general's son, code-named Galahad, falls under suspicion by the SS after a Nazi operation suddenly goes bad. In the middle of it all is OSS agent Cletus Frade, who knows the identity of father and son and what they will do... if they can survive that long. For not only are SS and Abwehr officers hot on their trails in both countries, but the OSS has branded Frade a rogue agent and is determined to shake the truth from him, at whatever cost. If Frade can't figure a way to hold them all off, then the futures of all three men may be very short indeed....