People from some UFO cult trying to kill Scully's sprog, William. Towards the end of the episode Scully asks to LGM to look after him and take him somewhere safe but no sooner have they left in the van than they are confronted with the would-be assassins who shoot at the van causing it to run off the road. While Frohike and Langly are dazed in the front, Byers finds himself on the wrong end of a gun in the back and William is taken.
Skip to next episode and...
The guys are looking at photos to ID the kidnapper but ignore the photo which matches.
Skip to...
Scully's apartment and the guys are trying to trace the mobile phone Byers stashed in Williams car seat. Reyes is not impressed and thinks Scully is making a mistake to trust them.
The guys finally pick up the signal they were looking for, unfortunately all they find is the car seat.
Skip to...
Scully meets with one of the men from the UFO cult. He offers to exchange William's life for Mulder's.
While Scully is talking to him, Frohike bugs his car so they can follow him back.
Skip to...
The guys are in the van, using some tracking stuff to follow the UFO guy. Unfortunately, Murphy's Law being what it is when it comes to our guys, they lose the signal. Stress and squabbling ensues. Frohike improvises and tells Scully to turn even though they aren't certain. Happily he guessed right and Scully finds the cult's headquarters destroyed and burning but William is unharmed.