Cap's search for the missing Falcon and Leila brings him and Texas Jack Muldoon to an asylum transported to another dimension, where he finds his friends without their memories and the small human colony on an asteroid under attack from alien monsters. Brother Wonderful and the Inquisitor, leaders of the Night People, open up a portal to Earth, planning to send the monsters there, but Cap is able to trick them and return the humans to Earth and blow up the asteroid as the creatures approach.
A minor story during Kirby's final run on Cap, but the art is really pretty, including the alien creatures who look like something out of a 1950s monster masterwork.
Frank Giacoia inks the 17-page story and cover.
This whole story, and much more, was recently reprinted in Captain America: Bicentennial Battles.