Eight years and $987,587,011 in box office loot later, the third and promised final chapter in the Night at the Museum franchise is upon us. A surprise hit (to say the least) when the Ben Stiller comedy fantasy opened in 2006, Night at the Museum represents the digitally realized dreams of a zillion kids (and their adult minders): You're roaming the musty exhibit halls of a history museum, past dusty dioramas and epoxied tyrannosaur skeletons, and find yourself imagining the ancient icons, the mummified critters, the taxidermied beasts come to life. Some of them even talk.

Night at the Museum: Secret of the Tomb starts in 1938 at an archaeological dig in Egypt, with a young boy falling into a sudden maw that opens in the earth. He discovers a pharaoh's tomb (or a forgotten Indiana Jones set?) and the Tablet of Ahkmenrah, a gold abacus-y thing whose magic powers are responsible for the vivification of the Night at the Museum's gang of relics.

A sandstorm and a hurried excavation and extraction later, Secret of the Tomb fast-forwards to the here and now and the American Museum of Natural History. Stiller's Larry Daley is overseeing the gala reopening of the planetarium. He's putting on a show for New York's philanthropic set that will feature Teddy Roosevelt (Robin Williams), Attila the Hun (Patrick Gallagher), the pinky-size jocular duo of Jedediah (Owen Wilson) and Octavius (Steve Coogan), and assorted dinos and deities. But then the characters go haywire, freaking out the fancy-pants celebrants and forcing Larry into a worried huddle with the museum curator (a smirky Ricky Gervais).

The tablet's magic is fading. Unless something is done to reverse course - and curse - Attila, Teddy, the cowboy, the emperor, the whole beloved Night at the Museum menagerie will turn to wax.

Like many a sequel that has exhausted its plot possibilities, Secret of the Tomb looks abroad to add color and culture. In this case, the action turns to a sister museum in London. That allows for the introduction of Lancelot, an Arthurian windbag played with shiny armor and a shine in his eyes by Downton Abbey's Dan Stevens, to Mindy, a museum security guard (Rebel Wilson). There's also Larry's Neanderthal doppelganger, a lug called Laa, who takes a third-act interest in Mindy, and vice versa.

Ben Kingsley, who plays one of the Israelite leaders running from the pharaoh's legion in Exodus, goes over to the other side, playing a pharaoh in Secret of the Tomb.

Speaking of third acts, they could have subtitled this swan-song installment The Long Goodbye - the resolutions and au revoirs take forever. It's sad, of course, to see Williams in his Rough Rider uniform and wire-rimmed spectacles, but his performance as the 26th president is ghostly in ways that have nothing to do with the actor's untimely death.

The Night at the Museum tent pole has played fast and loose with history, and with our knowledge, or lack of knowledge, of the past. But I'm pretty sure a capuchin monkey never urinated on teensy-weensy figures of a cowboy and a Roman emperor as they ran for their lives from a lava flow in ancient Pompeii. That happens in Secret of the Tomb, and it seems like a fitting way to retire the show.

Night at the Museum: Secret of the Tomb **1/2 (Out of four stars)

Directed by Shawn Levy. With Ben Stiller, Ricky Gervais, Dan Stevens, Steve Coogan, Owen Wilson, Rebel Wilson, Robin Williams. Distributed by 20th Century Fox.

Running time: 1 hour, 37 mins.

Parent's guide: PG (monkey urination, adult themes).

Playing at: area theaters.EndText