In the aftermath of the shooting, Fredo is nowhere to be found. Every Corleone button is out there on the manhunt, and Connie and Mama Corleone are with Kay comforting the children. Fredo doesn't show up until after Michael hand the reins over to Tom. He finally showed up to drag Deanna away after she sees the dead shooters, and he was still in his robe and pajamas.

Clear back to GF1, Michael had already questioned Fredo's loyalty, reprimanding him for taking sides with Moe Greene in the casino takeover dispute. He knew Fredo had poor self-discipline, from readily adopting the hedonistic Vegas lifestyle to allowing Moe Greene to smack Fredo around with no retribution.

As the pieces started to fall into place, notice how Fredo's tone becomes more nervous and agitated:

- After bringing the $2 million to Havana, Michael lets him know the Corleones are buying into Cuba. Fredo says he's nervous, and slips that "Havana's my kind of town." This from a guy who's supposedly there for the first time.
- Michael predicts his assassination and that Roth is behind it. Fredo's facial expressions indicate deception when he asks how he can help, and becomes much more high-pitched and nervous in his inflection. Contrast this to how calm and cool he is where he's introducing Michael to the Senators, and later how he tells about how Johnny Ola knew about all the great places in Havana.
- After that scene with Fredo and Michael, Roth tells Michael his sixth sense says that Fredo brought the $2 million. Michael never mentioned to Roth the logistics of the money making its way to Cuba, much less Fredo's role.
- Then at the New Year's party, Fredo can't even muster a coherent excuse for leaving the contingent.