When the ceremony to extract the symbiote from the last Ba'al clone ends in disaster thanks to the original Ba'al putting a fail-safe plan into action, Colonels Cameron Mitchell and Sam Carter and Dr. Daniel Jackson finds themselves being forced to flee to Earth back through the Stargate as they watch the reality that they know fall away while their teammates, Vala Mal Doran and Teal'c both mysteriously disappear into thin air with General Jack O'Neill also dying in the process. Now, trapped in an alternate timeline where their lives have taken different paths due to the Stargate itself never reaching the United States and ultimately the Stargate Program and Stargate Command never existing, Mitchell, Sam and Daniel must convince the government in that reality that they can change the past