P風暴 (P Storm) (Blu-ray release 2019-6-28) is the fourth Storm movie following Z Storm (2014), S Storm (2016) and L Storm (2018) about anti-corruption investigation in Hong Kong. This is a self contained and complete story, so it is not necessary to watch the previous movies first, although a villain originated from the first movie. This time the protagonist goes into a prison to carry out investigation – that’s why it is called P Storm.
While this prison idea is fairly interesting, the plot is not really believable and cannot be taken seriously. Nevertheless, it has enough entertaining elements in it with a well known cast. So each sequel got increasingly higher box office in mainland China.