The storyline features members of one of two factions, both capable of time travel, engaged in a long-term conflict called "The Change War".

New soldiers, entertainers, and medical staff are recruited by existing Change War participants from various places and times; characters include: Cretan Amazons, Roman legionnaires, eight-tentacled Lunans (natives of a civilization that thrived on Earth's Moon a billion years ago), Hussars, Wehrmacht Landsers, Venusian satyrs (recruited from Venus a billion years in the future), American GIs, and Space Commandos.

The Change War combatants and their facilities (places such as Field Hospitals, Express Rooms, Recuperation Stations, and Entertainment Spots), located within artificially-created bubbles of spacetime outside of the Universe, run on the Big Time.

However devastating this development is to 20th century humanity, now doomed to live under the worldwide oppressive and genocidal rule of Nazi Germany, in the context of the overall Spider-Snake cosmic conflict, this change was incidental and of only marginal importance.

Algis Budrys praised The Big Time (which he categorized as a play, not a novel) as evidence that Leiber was the only science fiction writer of his generation "who as a matter of course and conviction saw through the mores and circumstances which are now proving nonviable not only in commercial literature but in what we can call life as well", and a precursor to Roger Zelazny and Samuel R.