Dr. Walker was an acquaintance of Kristine Walsh, having met her at Gerald Ford's home to play golf on one occasion. After the Visitors arrived, Kristine saw him at the Medical Center, and he confronted her about her affiliations with the Visitors. He spoke of her as a Minister of Propaganda, and compared her to Joseph Goebbels, making references to the Nuremberg Trials as he denounced her of her lack of journalistic integrity and bade her good day. Unfortunately for him, Diana and Steven were present at that moment to witness this and had Brian and shock troopers abduct him.
He was taken aboard the mothership and subjected to the conversion process. After he was successfully brainwashed, he was later seen on the command deck, greeting Walsh warmly as he was seemingly delighted to see her. This action only furthered Kristine's distrust and suspicions regarding the Visitors.