“It’s nothing like the comic book you want it to be,” crusty old Calvin Barr (Sam Elliot) angrily tells the FBI agent played by Ron Livingston about his wartime exploits in “The Man Who Killed Hitler and Then The Bigfoot.” He might be speaking to all of us in the audience. The title of producer-writer-director Robert D. Krzykowski’s movie promises a wild and zany ride, but instead the picture turns out to be lethargic rather than wacky, and not so much over-the-top as numbingly leaden. It just proves the rightness of the old adage that you can’t judge a book—or a movie—by its cover.

The movie does provide a showcase for Elliot, whose career renaissance continues with a role that doubles him with Aidan Turner as the younger Barr, juxtaposing the latter’s experiences during the 1940s with his current recall to duty in old age. In his former days, it seems, Calvin was a shy guy working in a hat shop. That’s where he met lovely schoolteacher Maxine (Caitlin Fitzgerald), whom he wooed but never found the gumption to propose to before going off to war, where he was prepped by a hard-nosed Russian (Nikolai Tsankov) for a mission to impersonate a Nazi officer and gain admittance to the office of Hitler (Joe Lucas) and shoot him. He actually succeeds, though the war grinds in nonetheless, and he’s haunted by the killing, as well as the fact that Maxine died while he was away.

Now an aged fellow whose best friend is his equally decrepit golden retriever, Calvin is approached by that FBI agent and a Canadian scientist (Rizwan Manji) to use his legendary tracking skills to kill Bigfoot (Mark Steger). It seems that the critter has come down with an infectious disease that threatens all life on earth, but for some reason Barr is immune and can stalk the beast without danger of carrying the plague back to civilization. Much of the picture’s latter section is devoted to that mission, in which he again succeeds.

So you can say the picture is true to the title—just not to the spirit it suggests. It’s not without moments—a shot of a Nazi wristwatch near the start promises a jokey Zucker brothers vibe that never materializes, and the climactic battle with Bigfoot generates some excitement. Overall, though, the tone is oddly serious, and the pacing almost glacial. The mood of solemnity is accentuated by a subplot about old Calvin’s reconnection with his little brother Ed (Larry Miller), which is meant to be touching but seems merely slow.

To be honest, that approach works reasonably well for both Elliot and Turner, who together create a portrait of Calvin that recalls Jimmy Stewart in his younger and older phases. But the rest of the cast seems stranded. The pacing does allow one, however, to appreciate the attractive work of production designer Brett Hatcher and cinematographer Alex Vendler, along with the other craft contributors, including the effects team responsible for Bigfoot’s look as a more agile, dangerous creature than usual.

Despite all the care Krzykowski and his cohorts have lavished on “The Man Who Killed Hitler and Then The Bigfoot,” however, it emerges as an oddity that may draw in viewers with its outrageous title but will leave them complaining about a bait-and-switch by the close.