Step through the stargate with SG-1, a team of soldiers and scientists, as they travel instantaneously to other planets to explore, forge alliances, defuse crises, establish trade, investigate ancient mysteries and defend Earth from such hostile forces as the Goa'uld and the Replicators.

Prototype: The team finds an underground laboratory and a man frozen in a stasis pod - Khalek, a prisoner of a Goa'uld. But Khalek was not his prisoner - Khalek was his creation. Daniel's instinct is that if Khalek can't ever be confined safely, he should be killed before he can complete his evolution.

The Fourth Horseman (Part 1): Carter is determined to design a weapon that can defeat the Prior's superhuman powers. Daniel and Mitchell must track down a Prior, then hope that Carter's weapon really can suppress a Priors' powers. If it doesn't, and they fail, Earth's entire population will die with them.

The Fourth Horseman (Part 2): Landry begins to fear that SG-1 may be soon facing a global pandemic. Mitchell and Daniel return with a dazed Prior in tow. The team is shocked to receive the worst news yet when the captured Prior reveals the Oris horrifying master plan: to completely obliterate the Ancients.