Other reviewers have said enough about the plot, but it basically concerns how two parents react after the death of a beloved teenaged daughter.
I found the whole thing convincing, including some of the stupid, illogical things some of the characters did. That is what people do, after all.
The ending wasn't neat, and certainly not particularly happy - but why should it be? Things rarely are in real life, after all.
If there is a weak point, it is probably the inclusion of the Swedish actress Lena Endre. I don't know why, I just don't think she is a particularly good actress, or a massively bad one, yet she seems to pop up everywhere in Scandi films - and in this, she just seemed to be included to broaden the film's interest, making it saleable in the Swedish market.