Mulder and Scully learn that they aren't the only ones desperately searching for their long-lost son, William. The very fate of the world may depend on it.

A chilling secret is revealed when an old friend reaches out to Mulder and Scully in a seemingly impossible way.

Mulder and Scully rush to find an on-the-run William while the Cigarette Smoking Man pushes forward with his ultimate plan.