In 1976, Ronald Reagan becomes President of the United States, declares the U.S. will plant a base on the moon by 1980 and a base on Mars by 1989. The Iranian Hostage Crisis occurs, but Reagan issues a stronger response by rescuing the hostages within two weeks of it happening. As a result, Osama bin Laden rises to power earlier than he normally would have in the prime timeline. Meanwhile, The Soviet Union decides to build a starship that will travel to the stars because they want to one-up the United States. The ship launches, but soon becomes lost, while the Soviets pretend it isn't.
In the early 1990's the U.S. and the Russians join forces to find the Soviet starship, which leads the joint venture to the other side of the galaxy by means of a wormhole. When they attempt to return to Earth, they find themselves in the past, where they try to fix certain events in the past while they wait to re-route the Soviet starship and for history in general to catch up to where they launched the joint mission to begin with.
Things go wrong as events do not play out as planned and numerous cases of unintended consequences result from the multiple attempts at fixing the timeline.