An explosive James McAvoy does a jumped-up version of Denis Leary’s roguish “Rescue Me” character in “Filth,” a cop caper that more than lives up to its name.

McAvoy’s Bruce, a misanthropic detective whose sexy wife (Shauna Macdonald) is holding out on him until he gets a promotion, is trying to solve a murder while rampaging through the drugs, booze, porn and women of Scotland.

Writer-director Jon S. Baird has devilish fun with the hilarious black-comic elements of Irvine Welsh’s novel, but the incessant bad behavior does get a wee bit monotonous, and the twist ending is disappointingly pat. Still, McAvoy rules, showing again that the erstwhile Mr. Tumnus is one of the most vital and versatile actors of his generation.