Although no one knew what happened, and it was all speculation, it would be difficult for me to not believe that Arlene had killed Cord’s mother so that they could be together.
And when Cord did not grab the ‘gift’ she gave him, when Arlene realised she had done this for nothing, she killed herself.
The police can investigate, they can have their postulates and beliefs, and everyone can turn the episode into a dialectic.
But I know, from the moment I saw Arlene, that she wasn’t ‘right’.
Imagine a ten part drama. You watch what you think is the first episode, but it is the tenth. That is how it felt when I looked at Arlene that first time.
To me, she was somewhat unbalanced and believed with every atom that Cord balanced her. And when he withdrew, due to his mother, she fought to regain that balance. And if it took killing his mother, than that is what it took.
And when it was clear that Cord was never going to be her balance; she killed herself.