As the book is a thriller the cover should be a dark one, but as there is also hope in it there can be color in the cover.
Two children should sit together in a big green garden in front of a very big house. The house and garden don't need to be displayed in detail, they can be just shadows or you see parts of it, not the whole. I don't know if it is even possible to display it at all, because the focus should be on the children. The girl is cute with blonde hair and is playing with something (dolls, anything). The boy has dark hair and should hold a rope in his hands and tie knots in it. They look happy, the girl more than the boy. He looks more focused, quiet.
The shadow of the boy should be a big monster with piercing green eyes, so that you know that something isn't right with him. Or the boy has the piercing green eyes. The shadow of the girl should look lost/scared or she doesn't have a shadow, I am not sure about that. The side of the girl should be more bright, happy colors; the side of the boy is dark, dangerous, scary. In it should be a tree, where a dead cat hangs on a rope :( It shouldn't be obvious, maybe one can see it only on the second glimpse.
But this is only an idea, I’m also open for other ideas, as long as it is not a happy cover. There is violence and terror and sex in the book so the cover can be scary and awake feelings of fright and unease but not right in the face, more in a subtle kind of way. The main focus should be on the children and that there isn't something quite right with the boy.
Somewhere should be my name Ann Mmort. I am still thinking about the title (maybe ALONE for starters).
Thank you for your time and your ideas!