Jay Maidment, Marvel Studios
Chris Evans plays Captain America in CAPTAIN AMERICA: THE FIRST AVENGER, from Paramount Pictures and Marvel Entertainment.

The filmmakers took a risk planting "Captain America: The First Avenger" squarely — and I do mean "square" — in the period of the original comic book, which was published just six months before the United States entered World War II, beginning an enormously successful run that continued throughout the war years.

The iconic character's arrival was perfectly timed to coincide with a period of U.S. patriotism that was unlike any other. Aside from the obvious nonfiction venues, go back and read novels or peruse comics or listen to radio shows or watch movies and cartoons made from 1941-45 and you're bound to catch some of it.

Such propaganda wasn't in everything, of course, but it was in a lot — from a sidelong glance to a subtle subplot to a full-blown story line involving Nazi intimidation or Japanese terror or Italian oppression. Even in comedies, musicals and westerns.

Sure, Humphrey Bogart took on the Axis of Evil in a string of films, including "Across the Pacific, "Casablanca" and "To Have and Have Not," but so did Popeye and Donald Duck. Jack Benny made jokes about Hitler on his radio show, and every comic from Charlie Chaplin to Abbott & Costello ran into Nazis in movies. Even Sherlock Holmes battled the SS, for heaven's sake.

So Captain America arrived just in time, and he was arguably the most patriotic of all. Clad in a red, white and blue costume and carrying a huge round shield with the same color scheme, along with a large white star on his chest and in the shield's center, when he came to save the day, it was clearly the American way.

Making a superhero movie about this character in the 21st century, and keeping the World War II motif, must have been an enormous challenge to the filmmakers of "Captain America." But it comes off amazingly well.

Chris Evans (and his "Benjamin Buttoned" body in the film's first quarter) is terrific as Steve Rogers, a sickly weakling with a lot of heart who is super-sized by a secret serum. And Evans has great support from Tommy Lee Jones as an Army colonel, Hayley Atwell as an agent and love interest, Dominic Cooper as Howard Stark (whom "Iron Man" fans will recognize) and Stanley Tucci in an all-to-brief turn as the scientist who buffs up Evans' character.

Also good are the villains, Hugo Weaving as a Nazi scientist who is such a wild card that he makes Hitler nervous (late in the film he reveals himself as a mutant with a deep red face and flat nose — think Lord Voldemort with a sunburn), and Toby Jones as his neurotic sidekick.

The story is faithful to the origins depicted in the comic book, and the film's look and tone are perfect, a wonderfully retro, art-deco, Indiana Jones-ish adventure that is filled with action and excitement, and with a sharp sense of humor that is never overused.

There's even a delightful musical montage that has Captain America being camped up for use as a propaganda puppet — on bond tours, in movie serials, in comic books, etc. — that takes the movie outside of its fictional realm for a few moments, acting as a sort of mini-documentary about the actual evolution of the character during the early 1940s.

But there's also a missed opportunity.

The final moments are something of a cheat. As the movie closes, there's a sense that this wasn't a movie at all. It was instead merely a setup for another movie — next summer's "The Avengers."

As fans already know, "The Avengers," which opens in May, will feature Chris Evans as Captain America, along with other Marvel superheroes, including Robert Downey Jr. as Iron Man, Chris Hemsworth as Thor, Scarlett Johansson as Black Widow, Mark Ruffalo as the Incredible Hulk, Jeremy Renner as Hawkeye and, of course, Samuel L. Jackson as Nick Fury, who has appeared briefly in four pre-"Avengers" Marvel films, recruiting superheroes.

The manner in which Captain America finds himself in the 21st century is in keeping with the comic mythos; what happens to him did happen in the comics. But not until he'd had several years of adventures.

It's necessary for "The Avengers," of course, to get the good captain into the modern day with the other heroes, but it also means there probably won't be any more "Captain America" films, and that's a shame. It might have been nice to have a trilogy, with the last film using this ending — or non-ending. Hey, it's a Saturday matinee serial but there will apparently be no more chapters, at least in the '40s setting.

And that's a bit confusing to those not embedded in the mythology.

I saw "Captain America" with my wife and another couple, and none of them knew about "The Avengers." They all said they liked the film but couldn't help feeling let down by its unresolved conclusion and dangling plot points (chiefly the abruptly stalled romance).

And surely they can't be the only ones.

"Captain America: The First Avenger" had a big opening last weekend, but if it's going to keep up the pace, it needs to appeal to moviegoers outside its rabid fan base.