Complex sentence: A CIA agent contacts Mulder and Scully and tells them about a Russian assassin dispactched to eliminate evidence of Cold War-era Russian clones who had infiltrated the American medical establishment.
Split into simpler sentences: A CIA agent contacts Mulder and Dana Scully, and informs them about a Russian assassin. The killer had been dispatched to eliminate evidence of Cold War-era Russian clones who had infiltrated the American medical establishment.