One thing I've always been curious about:

Michael seemed frantic to get Fredo in his car as he was leaving Havana ("It's the only way out of here tonight...You're still my brother!!). And, the first thing he asks Tom after he returns and they're alone is, "Where's my brother?" But then he tells Tom to "Get word to Fredo..." etc. The urgency seemed to be gone immediately until after Michael testified and he told Tom, "I want to speak to Fredo."

What happened? Any ideas?