“Beneath the Surface” is episode ten of season four of Stargate SG-1.
SG-1 are working in an underground civilisation, which is sheltering from an ice age affecting their planet. They don’t know that they are SG-1, as all memories of their former life has been replaced with new ones and new names, although Teal’c does seem to possess some memories of it, but these are removed again.
All the workers are being kept in the dark, supporting an advanced civilisation that they do not even know exists. SG-1 have been also tampered with to make them willing workers, but the memories keep breaking through. SGC are in the meantime being lied to about what happened to SG-1, and they are getting suspicious..
The civilisation is going to regret matters. That’s a certainty.