Back in '87, Gibson and Glover's mismatched, bickering buddies, Richard Donner's loose-wristed direction and Shane Black's slick dialogue coined a harder edged style of action comedy. But Hollywood action movies have moved on since then, becoming more flippant, knowing and cynical. So how did it all turn out so well? In a word, familiarity... both in the sense of 'breeds content', and in the sense of familial relationships: here is a new sub-genre, the action-sitcom, in which the heroes' complicated emotional lives are as important as the gunplay, car chases and explosions. Glover's daughter is pregnant, but won't say who the father is; glamorous detective Russo, Mel's love interest from 3, is also pregnant, and she, like the audience, is waiting to see if the haunted Mel will finally bury the memories of his dead wife by asking her to marry him. On the action front, it's business as usual, but with creakier limbs. 'We're getting too old for this shit,' gasps Glover, as he and Mad Mel drag their ageing bodies around LA in pursuit of a Triad smuggling gang that's selling Chinese immigrants into slavery. The climactic streetfighting clash between Mel and coldly charismatic martial arts star Jet Li is a bone-crunching classic.