Sunday, October 11: Season 4, episode 24 "Gethsemane"

In which Scully has to identify the body of the deceased: it's Mulder.

Thursday, September 17: Season 3, episode 24 "Talitha Cumi"

Alien healers and human killers and vice versa...

Sunday, August 23: Season 2, episode 24 "Our Town"

Scully is captured...again...by some very old people at a chicken processing plant, and invited to dinner...

Sunday, June 24/Thursday, July 30, 2015: Season 1, episode 24 "The Erlenmeyer Flask"

...in which we first see the alien fetus and the end of "Deep Throat...for now, anyway...