New guy here with an observation.

Whoever opened the drapes had to have done it while Kay was in bed asleep, due to her surprise at seeing them open when she awoke. I would assume that only immediate family or possibly a maid could access the bedroom without arousing suspicion. I can imagine Fredo doing this, perhaps thinking it was merely a signal that he had pulled off his part in whatever scam he thought he was involved in. I still have a problem with the dead hitmen though. Who killed them? It couldn't have been Fredo unless he was a knowing accomplice to the assassination attempt. I don't think he was. If the guy who killed them could get away, why couldn't they all get away? Did Roth arrange it that way so that Michael would suspect Frankie?

This is a nice site! I've already found answers to questions that have bugged me for years.