When 13-year-old Henry Hart meets his hometown's celebrated crime-fighting superhero Captain Man, his life suddenly becomes anything but ordinary. Captain Man not only makes Henry his new sidekick, giving him the alias "Henry Danger", but also says that someday Henry will take over for him as Swellview's full-fledged superhero.

In the meantime, the sidekicking is just an after-school job, but it must stay top-secret all the time. Henry Hart has to figure out how to balance the two conflicting sides of his life and keep everyone - including his family, even his two best friends - from learning Henry Danger's true identity.