Dr. Aaron Baker worked in an abortion clinic in Syracuse, New York. He was the fourth of five abortion doctors who was killed by the alien bounty hunter.
Mulder became involved in finding Dr. Baker after the deaths of Dr. Prince, Dr. Buchanon, and Dr. Gayhart, all abortion doctors that died in separate arson fires.
After talking to suspect, Calvin Sistrunk and through a newspaper clipping, Mulder and Scully learn that someone had put out an ad to locate Dr. Landon Prince.
Mulder and Scully go to the Globe and Mail Newspaper located in Binghamton, NY, where they are able to access the voicemail calls and learn that someone has identified the man in the ad as Dr. Aaron Baker from Syracuse, NY.
Mulder makes a call to Special Agent Barrett Weiss in Syracuse and tells him to locate Dr. Baker, as he could be in great danger. When Weiss arrives at Dr. Baker's home address at 737 26th Street, he sees Dr. Baker arguing with someone but Wysse can't see who the other person is.
Inside the house, we see the bounty hunter slamming Dr. Baker against the wall and tells him, "Your plan will not succeed." The bounty hunter then kills Dr. Baker with the gimlet weapon.