It's not an actual thriller so don't go in expecting an underdog mum who uses her senses to solve a mystery or even a serious story at that. It's an art house cosy movie with quirky characters and the semblance of a mystery, which is not so much the centre of the story but a plot device for the characters and for us the audience to get to know them better. It's the kind of movie you put on when it's sunny and you've just had too much food. If you're even a minor bit interested in watching something serious, I wouldn't recommend this and instead ask you to go for some proper action/thriller instead.
Review of In for a Murder
