] Mrs. Dashwood is irresponsible, but she is not an idiot. Elinor's suspicions were just that, while Brandon was a first-hand witness to what happened to his ward. Even if Mrs. D. refused to believe it at first, eventually she'd have to do something about it - she does care about the happiness of her daughters! . . . You're right, though, that he finally told his story to the best person!

Brandon is indeed in a cruel spot. Whatever his choice, he fears he will make Marianne unhappy and that is what he would least wish to do. It seems incredible to us that he would not warn her mother, but it says something of his way of thinking that he seems to truly believe Willoughby could do the honourable thing. As you say, Brandon has seen the way W can behave and yet acknowledges that this time it might be different.

As for Mrs. Dashwood, I believe JA has already forewarned us as to what success Brandon might have in sharing his suspicions. Remember how Mrs. D responded to Elinor after W's abrupt departure that threw Marianne into such despair?

"You must remember, my dear mother, that I have never considered this matter as certain. I have had my doubts, I confess; but they are fainter than they were, and they may soon be entirely done away. If we find they correspond, every fear of mine will be removed."

"A mighty concession indeed! If you were to see them at the altar, you would suppose they are going to be married. Ungracious girl! But I require no such proof. Nothing in my opinion has ever passed to justify doubt . . ." Etc.

Yes, Mrs. Dashwood is concerned for the happiness of her daughters, but she will not allow herself to be persuaded to follow up on Elinor's doubts and actually berates her daughter for having them. What sort of reception might Brandon receive, I wonder? True, the evidence would be hard for her to deny, but she'd hardly thank him for producing it. Brandon's chances of intervening successfully in this way would be slim indeed.

] the child hasn't vanished off the face of the earth. Colonel Brandon is taking care of mother and child for now, but things like this have a way of coming back to haunt a person! What if the child later shows up on their doorstep, needing financial support, or just wanting to know its father? (I don't think this is just a 20th-century phenomenon!). How would Marianne feel finding out about this years later?

Barbara has already answered the last part very well. 8-) As to the first, I think Brandon, if he once saw that Marianne was lost to him, would take steps to try and see that such a meeting never took place. As you say, these things can sometimes come out in spite of all attempts to conceal them, but since his motive in all this is trying to shield Marianne, I think he would exert a considerable effort in this direction. Another cruel circumstance for him, but there it is.