"Leonard Betts" is the twelfth episode of the fourth season of the American science fiction television series The X-Files.

It was written by Vince Gilligan, John Shiban, and Frank Spotnitz, directed by Kim Manners, and featured a guest appearance by Paul McCrane as Leonard Betts/Albert Tanner.

The show centers on FBI special agents Fox Mulder (David Duchovny) and Dana Scully (Gillian Anderson) who work on cases linked to the paranormal, called X-Files.

Fox Mulder (David Duchovny) and Dana Scully (Gillian Anderson) visit the morgue, where they find Betts's head in a medical waste dumpster.

When an interior slice of Betts's polymerized head is examined, the agents discover that his frontal lobe displayed signs of pervasive cancer.

Mulder has Chuck Burks (Bill Dow) subject the slice to a Kirlian photography test; the final image shows a corona discharge that takes the appearance of human shoulders.

The agents visit his elderly mother, Elaine (Marjorie Lovett), who informs them that Albert died in a car accident six years previously.

[3] "Leonard Betts" was written by Vince Gilligan, John Shiban, and Frank Spotnitz and directed by Kim Manners.

[4] Scripts written by Gilligan, Shiban, and Spotnitz were humorously credited by the production crew to one "John Gillnitz"—a portmanteau of the three writers' names.

[7] Regardless, John Shiban considers "Leonard Betts" to be "a great X-Files story" and very important because it established the story-arc featuring Scully's cancer.

[9] Betts's character was supposed to be a "sympathetic" creature who "killed not out of vengeance or anger but for survival",[9] and director Kim Manners thus urged McCrane to perform with "emotional conviction.

Club's Emily VanDerWerff agrees, writing in her review of the episode, "It also helps that Leonard's such an understandably human monster.

"[12] Conversely, Amy Donaldson, in her book We Want to Believe argues that Betts's condition, in which he is "riddled with cancer" but can "see the sickness within people", is a metaphor for someone who "has let sin or evil become the regular course of life".

In the episode, Agent John Doggett, played by Robert Patrick, stumbles upon a creature that altruistically absorbs the diseases and ailments of others.

Donaldson argues that the soul eater is the polar opposite of Betts because it takes an illness in order to help a person, even though it hurts itself in the process.

Richard Edwards and Dean Kowalski, in the chapter "Some Philosophical Reflections on 'Trust No One'" of the book The Philosophy of The X-Files, argue that Scully withholding the knowledge of her cancer from Mulder is an example of psychological egoism in a protagonist.

She notes that what Scully and Burks mistook for tumors were actually blastema, or masses of cells capable of growth and regeneration into organs or body parts.

[21][22] David Lavery, in his book The Essential Cult Reader, argues that the Super Bowl switch that the series made with "Leonard Betts" in order to make the episode more appealing to non-viewers was instrumental in the trend that favored programs being aired sequentially later on during syndication.

Writing for Den of Geek, John Moore listed Betts as one of his "Top 10 X-Files Baddies", writing that "Fox had the Superbowl[sic], the Superbowl happens on a Sunday, Fox decides to run the show in the prime slot after the big game... [...] So, did, they soft-pedal things in order to grab a wider audience?

[23] Vitaris praised the episode's balance of humor and horror, noting "Although 'Leonard Betts' is not a comedy, the three writers take such pleasure in the story that you buy the situation.

"[23] Robert Shearman, in his book Wanting to Believe: A Critical Guide to The X-Files, Millennium & The Lone Gunmen, rated the episode four stars out of five.

"[24] Shearman also wrote that "Leonard Betts" was the first episode "to come along [in the fourth season] which feels light and frothy, and it deliberately makes the unkindest cut of all.

Connie Ogle from PopMatters ranked the character among the "greatest" monsters-of-the-week, describing him as someone who could "grow back his own head after being decapitated, a feat that resulted in the show’s best-rated episode.