There's a farewell feeling to "Night at the Museum: Secret of the Tomb," the third installment in the family-film franchise that began in 2006. Not just because museum guard Larry Daley, played by Ben Stiller, is trying to keep alive the magic that animates his favorite exhibits, but because "Secret of the Tomb" is one of the last times we'll see Robin Williams, who died this year.
"Secret of the Tomb" opens with Larry, now a high-level staffer at the American Museum of Natural History in Manhattan, realizing that something is wrong with his living displays. The tiny Roman general Octavius and his cowboy friend Jedediah (Steve Coogan and Owen Wilson) are becoming destructive; the prince Ahkmenrah (Rami Malek) keeps fainting; Teddy Roosevelt (Williams) starts spewing other presidents' quotes ("Heck of a job, Brownie!"). It turns out that their life source, an ancient tablet, is beginning to corrode.
There isn't much magic left in this franchise, either. As Larry looks for answers in London's British Museum, "Secret of the Tomb" scrambles for new ways to freshen up its premise, with mixed results. Ben Kingsley plays a pharaoh who is delighted to learn that Larry is Jewish ("We owned 40,000 of them!"), Rebel Wilson goofs around as a snarky British guard, and Stiller does double duty as a Neanderthal named Laaa. The most appealing new figure is Dan Stevens, of television's "Downton Abbey," as Sir Lancelot, who can't understand that he isn't really alive, let alone a fictional personage.
Like "Toy Story 3" and the final "Harry Potter" film, "Secret of the Tomb" tugs at the heartstrings. If you do find yourself choking up, it's probably because the film's themes of mortality and loss are underscored by Williams' death. It used to be easy to get irritated by the actor's sentimental streak -- the pursed smile, the misty eyes -- but here, donning granny glasses and a Rough Riders hat for the last time, Williams will get to you. "Secret of the Tomb" ends with a dedication to him and to Mickey Rooney, who briefly reprises his role from the original film.