The madness of appeasement

I agree that Myra was the villain (though she may not necessarily be aware of it). Billy was skeptical the whole time and was a complete pushover. In fact I think he was the only one who thought the entire plan through.

The key line in the movie comes when she asks why she married Billy. He says "I don't know dear. Why did you?"

She says: "Because you're weak. Because you need me."

He returns: "Those are both good reasons..."

In fact, she's got it backward. He's the strong one. She has listed the reasons he married her - or at least why he complies with her wishes. He loves her too much to abandon her (she alludes to the fact he once tried, but came back). He's motivated by guilt and a feeling of responsibility for her, because he knows she's in a delicate mental state.

Of course things go too far and he acknowledges the madness in adhering to her plan. He's been facilitating her madness and now can't seem to back out. For him, being caught in the end is a relief.

He is appeasing in order to avoid conflict, but not out of fear for himself. He avoids conflict to protect her, until he can't avoid it anymore and has to confront her with the death of their child.

It is a fascinating relationship and you're right - it does illustrate the fact that appeasement and collusion, enabling a sick mind in defiance of reality cannot lead to anything but doom.