Hold On!
NASA scientists regret their decision to let their children name America's next rocket when the kids suggest it be named after their favorite British rock band, Herman's Hermits. Worried about potential public outcry, NASA sends skeptical scientist Edward Lindquist to tail the Hermits on their California tour, after which they'll make the decision.
When the children of American astronauts choose "Herman's Hermits" as the "good luck name" of the next Gemini space capsule, NASA scientist Edward Lindquist is sent by U.S. State Department official Colby Grant to shadow the band on tour. His orders are to find out all he can about them to stave off a "P.R. nightmare". (Grant fears that putting the band's name on the rocket will make the world think the U.S. is "still a colony of Great Britain".)
Aspiring starlet Cecilie Bannister hires a publicity agent and photographer to take photos of her with Herman and the band, sure that this publicity boost will get her a new contract with a movie studio. They take an unflattering picture during a riot of teenage girls at Los Angeles International Airport but the misleading story in the newspapers leads Lindquist to believe that Bannister is an "old friend" of Herman's. Likewise, Bannister believes that Lindquist is a writer and part of the band's entourage as they pump each other for information about the band that neither of them really has.
Herman and his bandmates, mobbed wherever they appear, are sequestered in their rooms at the Miramar Hotel by their manager, Dudley, in advance of a charity benefit performance. Herman sees teens playing on the beach and wishes he could be one of them, meet the girl of his dreams, and fall in love. Mrs. Page, the benefit organizer, introduces Herman to her daughter, Louisa, who offers to show him the sights of Los Angeles. Denied by Dudley, Herman and the Hermits sneak off to Pacific Ocean Park where they split up, reasoning correctly that if they don't stick together, nobody will recognize them. Herman finds Louisa and falls in love while the other band members explore the park. Believing that the boys have been kidnapped, Dudley calls in the police.
Lindquist and Herman meet up again on the roller coaster and the scientist realizes than Bannister has been feeding him false information. Cleared of the kidnapping charges, Lindquist comes clean to the band about his mission and they arrange to have Grant see the band perform at the charity benefit. When teens overrun the country club, the mayhem convinces Grant to cancel the rocket naming but nationwide teen protests force NASA to name the capsule "Herman's Hermits". During a climactic concert for 50,000 fans at the Rose Bowl, the band is whisked by hypersonic jet to Cape Kennedy for the rocket launch and back in time to finish the concert and play one more song before the credits roll.