Plot summary
When two fathers on opposite sides of the country are inexplicably murdered at exactly the same time in exactly the same way, Mulder and Scully find that their eight-year-old daughters are perfect twins and were created in order to continue The Litchfield Experiment, a eugenics project of the 1950s which produced cloned boys named Adam and girls named Eve who have heightened strength and intelligence, but are prone to psychotic behavior.
Credits
Adapted from Wikipedia contributors, The X-Files season 1. HTML formatting and reference markers removed.