Suffix まい in this context

Question

... この事がお母さまに或いは悪い祟りをするのではあるまいかと、心配で心配で...

Kazuka is wondering about if she caused a curse to happen to her mother by burning the snake eggs. I understand the general meaning but the suffix "mai" confuses me a little bit.

It's a suffix used to convey a negative meaning, right? ie. 'probably isn't' or 'musn't'. But here, it is challenging for me to understand why the author used it. It feels like it weakens the possibility of Kazuka harming her mother, but we know that she is anxious about her actions. Or is it used here to strengthen the if clause?

This is "The Setting Sun" by Osamu Dazai by the way.

Answer 1

まい is a negative inference/volition marker, and あるまい is interchangeable with ないだろう/なかろう.

犬ではあるまい。
= 犬ではないだろう。
= 犬ではなかろう。
= It's probably not a dog.

But when they are followed by か, the meaning is switched. (If you know ではない(の)か, this is in the same vein.) See also Difference between だろうか and ではないだろうか.

犬ではあるまいか。
= 犬ではないだろうか。
= 犬ではなかろうか。
= It's a dog, isn't it?

Your sentence can be rephrased to 祟りをするのではないだろうか, so she is thinking it is likely to cause a curse.