“Touchstone” is episode fourteen of season two of Stargate SG-1.
SG-1 visited a planet called Madrona whose weather was controlled by an alien device called the Touchstone. When they return to take a better look, and hopefully figure out how it works, they discover that the Touchstone has been stolen and the weather is quickly deteriorating.
SG-1 are blamed for the theft, as the thieves were dressed in their uniforms and used the stargate. They didn’t steal it, but when they return to Earth it’s quickly discovered that there are some rather disturbing weather problems happening. It looks like whoever stole the Touchstone used the second stargate discovered on Earth in “Solitudes”.
It appears that elements back on Earth are willing to take any technology, no matter what the consequences. Not surprisingly, Colonel Maybourne – who is so often involved in morally dubious activities – rears his head again.
As a result, most of this episode takes place on Earth.