The secret "Agency" in Washington D.C. sends Gabe Logan and his partner Lian Xing around the world to investigate a recent outbreak of viral weapons by a German terrorist named Erich Rhoemer. They go to New York City, and many places in Russia to end these actions. Also, PHARCOM a biotechnical corporation that was helping investigate these viral outbreaks is thought to be involved. Syphon Filter is a super weapon that if gotten into the wrong hands may bring the entire world under terrorist control, but who's funding it?