It flashes between the past when she was in high school to the present, 25 years later. Louise is now divorced from her husband. She's concentrating on raising their son. Until one day she gets an odd friend request from an old school friend, Maria.

Louise would have wanted nothing more than to make up for the past, for how she regrets how badly she and her friends back then, had treated Maria. The two start communicating via messages, but then the unsettling comes into it.

How could this be Maria communicating with her. Talking about the past when Maria seemly had disappeared and apparently died 25 years prior?
Is Maria back from the dead, or is this some cruel trick being played upon her?

It was interesting. For me, I felt the flashbacks were kinda slow. I wanted things to start happening, but I knew that would come. I was more interested in the present and what was going on.
As the truth about the night maria disappeared comes into effect, I guess I kinda always saw it coming. Her relationship with her ex husband, how he was back in high school, and the rumours about Maria back then.
I guess it was predictable that he was involved..... that he was the one who killed Maria back then. And that these messages, not just Louise has been getting, but some of her classmates too, have not been coming from Maria after all, but rather her mother who always suspected and blamed her daughter's classmates for what happened to her all those years ago.

The end was quite traumatic, as Louise gets the truth about what happened, and if she knows the truth, she has a feeling she might not survive it.

Her life almost comes to an end, but gets a reprieve and her husband skips town, Louise doubts she'll see him again. But all she cares about is her son being safe.. and to live in the present. If he comes back, she'll have to deal with it then, but I can't see that happening.

Why did he kill her? And what were the rumors? And I take it they never found her body?

The rumours were that at her old school, that she was easy. That she was into things. And he was messing around with her one day in the woods, thinking she liked it this way. So after he was done, she got up, spat on him saying he raped her. He didn't see it that way, but he couldn't have people thinking he was a rapist, it would wreck his life. So he caught up to her and had to make her quiet. So he made her quiet.

Then he had to move her, so he took her over to the cliff. And then laid her there. He would have left here there, but then saw she was still alive, and contemplated then calling for help, but then he thought back to her words, so he pushed her over the cliff and into the water, but not without taking her necklace. That's the one thing people would identify her with.
So she would just be bones now, wherever the body might be. But they never found her. her body could be half way across the world for anyone knew. Or just sank to the bottom.