"Bad Blood" is the twelfth episode of the fifth season of the American science fiction television series The X-Files.

Written by Vince Gilligan, directed by Cliff Bole, and featuring guest appearances from Luke Wilson and Patrick Renna, it aired in the United States on February 22, 1998, on the Fox network.

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.

"Bad Blood" was inspired by an episode of The Dick Van Dyke Show in which the main characters tell different versions of a fight they had.

Afterwards, he and his FBI partner, Special Agent Dana Scully (Gillian Anderson) must report to Assistant Director Walter Skinner (Mitch Pileggi).

The agents travel to the small town of Chaney, Texas, where they meet Sheriff Hartwell (Luke Wilson), whom Scully finds highly charming.

When she finds that the second victim had also ingested chloral hydrate in a pizza, she realizes Mulder is in danger and returns to the motel room.

In his recollection, he is sensitive and polite to Scully, while she is dismissive and irritable, and clearly enamored with Sheriff Hartwell (who, in Mulder's version, is far less refined and has obvious buck teeth).

Scully belatedly realizes she has been drugged, and before she loses consciousness, she sees Sheriff Hartwell's eyes turning green.

[1] (The series would later explore the idea of an X-Files crossover in the guise of non-fiction with the seventh season episode "X-Cops", also penned by Gilligan.

)[2] With the help of executive producer Frank Spotnitz, Gilligan came up with a new idea inspired by an episode of The Dick Van Dyke Show, called "The Night the Roof Fell In", in which the main characters, Rob and Laura Petrie, tell different versions of a fight they have had.

[1] Luke Wilson was cast to play Sheriff Hartwell; he had previously starred in the comedy film Home Fries (1998), which had been scripted by Vince Gilligan.

Wilson and Renna were fitted with faux vampire teeth—which were sardonically labelled "funny fangs"—courtesy of special effects makeup coordinator Toby Lindala.

In order to create a suitable model for the bite marks, Gilligan bit the back of his hand "to show [Basham] exactly what he wanted.

"[3] According to Susanne Kord and Elisabeth Krimmer, "Bad Blood" explores the dynamics of the relationship between Mulder and Scully by "develop[ing] the dysfunctional potential of [their] routine interactions.

[5] Michelle Bush, in her book Myth-X, described the episode as allowing the viewer "a peek inside [Mulder and Scully's] heads" by showing how they see themselves and each other, as well as "their insecurities about their attractiveness to the other".

[12] In a 2008 review of the Revelations DVD, which contained "Bad Blood", Erik Henriksen of The Portland Mercury praised the way the writers "managed to tweak their genre formulas" and said of the episode, "It's witty and quick and features a great performance from Luke Wilson".

[10] In a review of Revelations for the Reading Eagle, Gina McIntyre called the episode "a hilarious riff on how [Mulder and Scully] view each other".

"[14] Robert Shearman and Lars Pearson, in their book Wanting to Believe: A Critical Guide to The X-Files, Millennium & The Lone Gunmen, rated the episode five stars out of five and wrote "Now that's how you tell a vampire story!

Shearman and Pearson noted that "the gimmick here isn't supernatural, but structural", and called the episode's framing device "subtly done", which resulted in its "brilliance".

"[19] Den of Geek writer Juliette Harrisson named it the "finest" stand-alone episode of season 5 and wrote, "for sheer fun and narrative playfulness, the winner has to be Bad Blood".