“Angel Has Fallen” is the final chapter of a trilogy that we never really knew we needed.

The latest installment of the adventures of secret service agent Mike Banning (Gerard Butler) is an absurd, ridiculous walking contradiction that manages to be entertaining on its own terms – because it knows its lane and stays in it.

After stopping terrorist attacks inside the White House and in London, “Angel Has Fallen” finds Banning coming to terms with his own mortality and contemplating hanging it up to spend more time with his wife and daughter. (I guess the fact that terrorist attacks keep happening on his watch isn’t a red light that maybe he needs a new profession.)

Just as he appears ready to walk away, President Allan Trumbull (Morgan Freeman) offers him a promotion. While Banning weighs that option, Trumbull is a target of an assassination attempt – with Banning framed for the crime.

That leaves Banning as a fugitive from the FBI desperate to clear his name. With the help of his estranged father (Nick Nolte), Banning tries to hunt down the real culprits and protect Trumbull from more attempts on his life.

“Angel” is about as predictable as it comes, with even the surprises rather unsurprising. But the action sequences are so well staged and Butler sells his character so well I found myself invested in his plight.

The film is credited to five writers, which comes as no surprise with the way the story is all over the map. “Angel” is the kind of movie where the main character battles the effects of concussions and ponders if all the violence is worth it, then proceeds to take out entire squadrons of bad guys with direct shots to the head (while avoiding most of the bullets himself).

Butler at least makes the broken-down tough guy believable and his relationship with Freeman, who gets very little screen time here, feels authentic as well.

You get some other familiar faces in the supporting cast, including Jada Pinkett Smith as an FBI agent (no, really) and Tim Blake Nelson as the vice president, but they are all upstaged by Nolte’s scene-stealing dad – a conspiracy theorist who has gone completely off the grid. The only way this role could have been any more entertaining is if Randy Quaid had played the dad.

That father-son relationship is the heart of what is good, and bad, about “Angel Has Fallen.” Their banter is fun, and you can’t help but be entertained even as you realize it’s all pretty silly and over the top.

If you go in with the understanding that “Fallen” isn’t trying to be anything but mindless entertainment, you might be surprised by a film that exceeded my very low expectations.

It may not be high quality, but there have definitely been a lot worse action films and way worse sequels this year than “Angel Has Fallen.”

Starring: Gerard Butler, Morgan Freeman

Directed by: Ric Roman Waugh

Rating: R for violence and language throughout

Playing at: Regal Bowling Green Stadium 12, Regal Greenwood Mall Stadium 10, Highland Cinemas (Glasgow)

Grade: B-