Mason Fairbanks is a treasure hunter, and former lifeguard, who was thought to be the biological father of Homer, after sending love letters to Mona Simpson.
Disguised as a reporter, Homer tracks him down after he discovers old love letters written by Fairbanks to his mother, Mona, and begins to believe Fairbanks may be his biological father. After confessing his true reasons for seeking him out, Homer bonds with him, as well as Bart and Lisa, prompting Grampa to demand a paternity test. When the test reveals Fairbanks to be Homer's father they celebrate with an underwater treasure hunt, but goes wrong when the submarine Homer is in gets trapped between rocks. In his final moments, Homer reminisces about the many nice things Abe had done for him growing up, only to be rescued by Fairbanks. When he wakes up, Abe admits to having switched DNA samples during the paternity test, wanting to preserve the happiness Homer had been feeling with Fairbanks.