What's left is a rather humdrum thriller, with a thin plot and overwrought performances.

Pity McAvoy, who was left to improvise.

It's a thinly plotted affair, because it needs to be, and its narrative shortcomings eventually spoil the fun.

For all its solid ingredients, the final formula of My Son is let down by a wandering script. You end up with this jumbled up mess of a movie that goes from harrowing, sincere drama to over-the-top revenge thriller. It just doesn't sit right.