In the mid-21st Century, a top-secret consortium of corporations and governments have made time travel possible, only to realize that intruding on the past has been a terrible mistake. At the program's outset, a thousand scientists, engineers and support staff were confined to a subterranean complex where a corporate contributor specializing in artificial intelligence equipped apartments with Happy Home Companion software. Time traveler Marta Hamilton had little enough tolerance for other people intruding in her life, much less a software Dear Abby, so Marta bullies her Happy Home Companion into silence. At last convinced of the grave dangers time travel represents, government overseers suspend operations. Only the Happy Home Companions remain. Marta and fellow traveler Marshall Grissom hope they can finally leave the past behind, but when a federal judge is murdered, they understand their vulnerability to horrible manipulations by future counterparts. Marta and Marshall return to the Arizona desert where they confront a Happy Home Companion cult of vengeance, the outlaw Gillis Kerg, and an evangelical zealot waging a war on science.