Fredo may not have been the brightest bulb in the box, but no way did he even suspect he was set-up and wouldn't have been stupid enough to continue the fishing trip had he known. Actually, I agree with Apple. When Anthony was called back, Fredo was obviously disappointed, but had no clue of what was to happen.
TIS
"Mankind must put an end to war before war puts an end to mankind. War will exist until that distant day when the conscientious objector enjoys the same reputation and prestige that the warrior does today." JFK
