There But for the Grace of God

While investigating P3R-233, Daniel stumbles across a device that projects him into a parallel dimension. In this universe, Carter and O'Neill are engaged, and Teal'c is still First Prime of Apophis. Using the knowledge "our" Daniel has, the SGA launches a nuclear attack on Chulak through the Stargate. This results in a counter-attack as the Goa'uld send a horde of Pyramid Ships to destroy the parallel Earth, and Teal'c refuses to be swayed by those who wiped out his family. The parallel SGC (known as the SGA) must somehow dial out of their Stargate and get Daniel back to the planet so he can return to "his" universe.