After the Tahoe shooting, Michael tells Tom, "At his moment you're the only one I completely trust." I and others here believed Michael. Now, I'm not so sure about "completely":

At that moment, Michael needed Tom more than he had since the Great Massacre of 1955. But he needed Tom on his terms, under his control. In one of the most sublte and brilliantly acted scenes in the Trilogy, Tom starts out by asking, "Mikey, you all right?" Michael, unruffled despite his hair-raising escape from death, moves right into his agenda:

"There's a lot I can't tell you -- and I now that's upset you in the past." Tom gives a shrug--uncannily like the one Vito gave Bonasera when he said, "Be my friend...", as if it were some minor nuance. But, just as Vito was waiting for the clincher, "...Godfather," and the hand kiss, Tom was waiting for his reward: ..."it's because I admire you and I love you that I kept things secret from you... Tom, you're my brother."

Bada BING! Tom not only gets his emotional reward, he practically weeps with gratitude: "{I always wanted to thought of as a brother by you, Mikey -- a real brother." Now Michael has not only reinforced Tom's loyalty, which he assumed, but his fealty, which was not a sure thing, given the miserable way he'd been treating Tom. And, with no further ado--and no more information than he'd given Tom earlier--Michael puts Tom in charge so he can clear up the mystery.

So, getting back to the theme of this thread, if Tom's the only one Michael can completely trust, why is he still saying, "There's lot I can't tell you"? I emphasize the present tense because you'd think that if he's putting Tom in charge, he ought to have said, "couldn't tell you" and have confided in Tom. By then, Michael was pretty sure Roth was behind the shooting. But, when Tom asked, "If we catch these guys do you think we'll be able to find out who's backing them?", Michael simply demurred: "Unless I'm very wrong, they're dead already. They're killed by somebody close to us -- inside. Very, very scared they botched it." And Michael doesn't rule out Rocco and Neri, who could have squashed Tom like a bug while Michael was away. All Michael says is, "Anything is possible.

My question: why didn't Michael tell Tom more? Tom knew he was in deep with Roth and Ola, and about Pentangeli's troubles. Did Michael believe that if he told Tom he thought Roth was behind the shooting, Tom be tempted to help Roth to turn the tables on Michael for being left out? And, since Michael couldn't rule out Neri, Rocco or even Fredo, did he fear that Tom would start trying to figure out how they might have been in cahoots with Roth--and possibly being killed by them, or tempted to fall in with them--instead of being totally vigilent about protecting the family?

All in all, seems like less than complete trust to me. Your views?