The agents encounter two girls who look identical and whose individual fathers were murdered in similar, odd circumstances at the same moment over 3,000 miles apart.
Greenwich, CT: A jogging couple finds eight-year-old Teena Simmons sitting dazedly in her front yard - and her father Joel dead. FBI headquarters, the next day: The report says death by hypovolemia - Joel Simmons had lost over 75% of his blood. Teena claims to have no memory of what's occurred; physical evidence was washed away by rain. The Medical Examiner found traces of digitalis, a heart stimulant made from the plant of the same name (a.k.a foxglove), which can be used as a paralytic drug. Mulder notes the wounds and blood-removal resemble those of "alien" cattle mutilations.
Fairfield County Social Services Hostel, Greenwich. Teena tells the agents of red lightning yesterday, and of men from the clouds. The agents learn of an identical murder outside San Francisco, in Marin County: Doug Reardon died of hypovolemia at 2:30 p.m. PST - the same time as Simmons. Daughter Cindy, returning tomorrow from Sacramento with her mother, has said she remembers nothing.
The Greenwich hostel, 12:35 a.m. EST: Teena is abducted. Later that day, Marin County: Mulder and Scully discover eight-year-old Cindy looks exactly like Teena. When the agents show her mom a photo of Teena, she states Cindy is her only child - indeed, she and her husband tried for six years to get pregnant, finally choosing in vitro fertilization at the Luther Stapes Center for Reproductive Medicine in San Francisco.
Working on the idea that Cindy will also be kidnapped like Teena, Mulder and the San Francisco bureau stake out Cindy. Scully meets with a Dr. Katz at the Staples Center, who says Mrs. Simmons was treated by Dr. Sally Kendrick, a resident who earned a Yale medical degree after completing her doctorate in biogenetics. However, the center believed Kendrick was conducting eugenics experiments, fired her, and asked for a federal investigation - yet the Dept. of Health wouldn't investigate.
At their hotel, Scully gives Mulder the information, but he rushes her out after a phone call of only clicks - a signal to meet Deep Throat. He tells Mulder about the classified "Litchfield" experiments. In the 1950s, the Soviets were performing eugenics experiments trying to create a super soldier. The U.S. followed suit at a compound in Litchfield, Connecticut. Boys were codenamed Adam, girls Eve. Deep Throat arranges for the agents to see the adult Eve 6.
The straitjacketed woman looks exactly like Kendrick. She says that the Eves are prone to suicide and the only remaining Eves are her, Eve 7 who escaped as a child and Eve 8 who escaped ten years later. Each Eve has 56, rather than the normal 46, chromosomes, having extra pairs of chromosomes number 4,5,12,16 and 22 - which, she says, produced additional genes, heightening strength, intelligence, and psychosis. Mulder believes Kendrick cloned herself to produce Cindy and Teena, and that Eves 7 and 8 killed the parents to raise the girls themselves.
During their stakeout, Scully and Mulder can't prevent Cindy from being kidnapped by an adult Eve, who escapes in a light blue 1993 Corolla - switching to a dark blue car by the time she reaches Port Reyes National Seashore. Identifying herself as Kendrick, she introduces the girls to each other. She'd always keep watching them, she says, while also searching for the remaining Eve; the girls' recent murders forced her hand. She'd hoped to correct the Litchfield flaws, saying the Eves developed homicidal tendencies at age 20. Yet she herself was raised by a Litchfield genetic engineer in a good environment with medication. Then she begins shaking: The girls have slipped four ounces of home-grown digitalis extract into her soda. Police and FBI burst in, the motel manager had alerted them about a woman fitting Kendrick's description. Kendrick is dead, and the girls are cowering together in a corner, saying that this lady and another wanted them to take poison.
Scully and Mulder, driving the girls to social services, pull into a truck-stop diner - where Cindy spikes the agents' diet sodas. Unfortunately, Mulder forgets his keys and when he returns to the counter to fetch them, he notices a green liquid there: poison. He warns Scully, and the girls escape amid the tractor-trailers. When Mulder corners them, their screams bring help from a trucker. As Mulder searches for the girls, the diner waitress tells him that a school bus full of kids just left. After the agents' car speeds away, following it, the girls come out of hiding only to be caught by the clever Mulder. The girls, labeled Eves 9 and 10, are eventually sent to Whiting. When Eve 8 visits dressed as Kendrick, they exchange a chilling look of mutual knowledge.
- This installment was initially devised by freelance writing duo Kenneth Biller and Chris Brancato. "Ken and Chris came in and pitched a bunch of stories," remembered Glen Morgan. (Cinefantastique, Vol. 26/27, No. 6/1, p. 41) This story idea, about a genetic experiment involving identical sets of twins, was originally called "The Girls From Greenwich". ("Chris Carter Talks About Season One Episodes: Eve," TXF Season 1 DVD special features) This name is obviously similar to the title of the film The Boys from Brazil, a movie which The X-Files Magazine Yearbook 2002 (p. 57) cites as having inspired this installment.
- This episode was chosen to be realized a while after it was first suggested. Glen Morgan continued, "'Eve' was picked up for production when the regular writing staff had arrived at a point when a script was needed, and no one had one ready." (Cinefantastique, Vol. 26/27, No. 6/1, p. 41) Morgan ended up doing an uncredited rewrite of the episode with writing partner James Wong. (X-Files Confidential, p. 56)
- This episode's script went through five drafts. These were dated 25th and 28th October as well as 2nd, 3rd and 4th November 1993.
- The hardest location to find for this episode's production was a "typical" American-style roadside diner, a form of building very rare in Vancouver. Additionally, a parking lot including semi-trailers was required to be outside the café. This filming location was needed to represent the Hi-Way 49 Cafe, which was ultimately shown using Seacrest Motel and White Rock Sunset Café, in White Rock, the latter of which had a large gravel parking lot. (X Marks the Spot (On Location with The X-Files), pp. 31 & 40)
- Although The X-Files' producers originally searched for twins in Los Angeles, they were forced to cast local talent in Vancouver, as child-labor laws meant that flying the children there, in light of the limited number of hours they could work, would have made the episode virtually impossible to do. (The Truth Is Out There: The Official Guide to The X-Files, p. 127)
- Since finding twins who could act was proving to be challenging, Co-Executive Producer R.W. Goodwin at one point briefly considered an alternative solution. "I thought we should cast one actor and then do a photo double and split screen," he revealed, "but there was so much with the two of them together that it was impossible. It also would have been very expensive." (X-Files Confidential, p. 56)
- With much enthusiasm, Art Director Graeme Murray designed an awning for the exterior of the White Rock Sunset Café. More than ten semi-trailers filled the parking lot outside the café, prior to a ceaseless evening of filming. Noted Location Manager Louisa Gradnitzer, "Many of the drivers were a bit disgruntled by the 4 a.m. wrap time." (X Marks the Spot (On Location with The X-Files), p. 40)
- The editing of this episode turned out to be a struggle. "Instead of being fluid," observed James Wong, "it became a difficult editing exercise, to make it all flow right." (Cinefantastique, Vol. 26/27, No. 6/1, p. 41)
- Popular contemporary rock group Eve 6 named their band after this episode. The drummer was very impressed with character Eve 6's dialogue of biting somebody's eyeball.
- Eve 6's line, "She is me, I am her, and we are all together," is a clear reference to The Beatles song "I Am the Walrus". The lyrics of that song begin with the line, "I am he as you are he as you are me and we are all together."
- The footage shown on television in this episode (showing cartoon cats and the following news segment) was taken from Eek! the Cat. The same footage also appears in the Season 3 Millennium episode "Human Essence".
- The twin girls in this episode, Teena, and Cindy were named after the wives of Glen Morgan and James Wong. (The Truth Is Out There: The Official Guide to The X-Files, p. 127)
- In this episode, one particular setting and an arrangement of scenes therein seem surprisingly similar to some from the 1994 movie Pulp Fiction. When Scully and Mulder visit Cindy Reardon's mother, it's almost the same setting and camera work as when Christopher Walken's character is talking to the mother of Bruce Willis' character.
- Glen Morgan and James Wong were left with the impression, due to this episode's difficult editing process, that the installment could have been much scarier than it is. Harriet Harris' performances in this outing were what made the episode a success in their opinions. "She was great," declared Morgan. "Tremendous, terrific," Wong added. (Cinefantastique Vol. 26/27, No. 6/1, p. 41)
- Chris Carter described the rewrite which James Wong and Glen Morgan did on this episode as "interesting." (X-Files Confidential, p. 56) "'Eve' was an amazing episode," Carter expressed, "because it was beautifully rewritten [....] Morgan and Wong [...] did a fantastic rewrite job." (The Complete X-Files: Behind the Series, the Myths and the Movies, p. 43) He also stated Director Fred Gerber "brought some interesting stuff to it." Carter went on to say, "I liked the episode, the casting in particular, with the twin girls [....] Also Harriet Harris was excellent." (X-Files Confidential, p. 56) Elaborating on his thoughts about the twins' performances, Carter said, "Those two little girls were wonderfully understated and creepy." (The Complete X-Files: Behind the Series, the Myths and the Movies, p. 43) Particular scenes of this episode which Carter regarded as high points are the teaser scene, with its view of a dead father slumped in a swing set and the scene in which Mulder and Scully visit a restrained Eve 6. Carter remarked, "I love the teaser [....] It's kind of a horrific image and not something you see on your regular network TV show." Considering the visit Mulder and Scully pay to Eve 6 in an insane asylum, Carter opined, "I think it's a great scene." ("Chris Carter Talks About Season One Episodes: Eve", TXF Season 1 DVD special features)
- R.W. Goodwin was similarly thrilled with this outing. He enthused, "We just got very lucky that we found these little girls who were terrific. 'Eve', like most of the scripts was so goddamned good that our job was not to screw it up. If we can do it without screwing it up and deliver what's on the page, we're going to have a good show. 'Eve' in particular was a very good show." (X-Files Confidential, p. 56)
- The production delay which resulted in this episode's script eventually being used for production also caused a three-week interval between the airing of new episodes. (The X-Files Magazine Volume 1, Issue 11, p. 31) This episode aired after that interval.
- On its initial airing, this episode achieved a Nielsen household rating of 6.8, with an audience share of 12. This means that roughly 6.8 percent of all television-equipped households, and 12 percent of households watching television, were tuned in to the episode. It was viewed by 6.4 million households. (The Truth Is Out There: The Official Guide to The X-Files, p. 248)
- Cinefantastique (Vol. 26/27, No. 6/1, p. 41) scores this episode 3 out of 4 stars. The magazine comments, "'Eve' is a real nail-biter [....] The suspense comes when the audience learns the truth before Mulder and Scully do, and watches as the nasty little girls plot the unwitting agents' demise. One good twist is that Mulder, who is sure at first this is related to alien-caused cattle mutilations, for once turns out to be wrong [....] Functioning merely as a source, [Deep Throat's] [...] appearance seems superfluous. It's an awkward scene, obviously written to propel the story forward when Mulder, and the writers, are at a dead end. Acting honors go to Harriet Harris [....] Her scene in the insane asylum is unforgettable. Eyes popping, teeth snapping, restrained like an animal, she is Hannibal Lecter with a twitch."
- The X-Files Magazine (The X-Files Magazine Volume 1, Issue 11, p. 31) once described this as "one of the twistiest, scariest and smartest [stories] of the first series."
- In his reference book Wanting to Believe: A Critical Guide to The X-Files, Millennium and The Lone Gunmen, writer Robert Shearman gave this episode 4 out of 5 stars. He remarked, "Part of 'Eve''s cleverness is that it turns our expectations right on their heads [....] The result is that we get a mystery which actually intrigues and surprises the viewer. I'm naturally scared of children anyway – who knows what's going on in those little heads? – so 'Eve' had me chilled from the start." Shearman went on to praise the performances of the Krievins twins and Harriet Harris. "The only fly in the ointment," he criticized, "is the characterisation of the regulars, possibly because this is the first episode written by freelancers [....] The glee with which [Mulder] [...] finds out a little girl has been abducted just because it bolsters one of his theories feels very off-key. And Scully is rather colorless here – besides needing to have in vitro fertilization explained to her, the good doctor is told by Mulder, of all people, the function of the heart! Jerry Hardin, too, looks a bit all at sea; back to a role of genial provider of exposition for no obvious reason, his performance becomes awkward and unusually mannered. It's a clever story, though, [...] [showing] elegance and guile."
- Harriet Harris as Dr. Sally Kendrick, Eve 6, and Eve 8
- Erika Krievins as Cindy Reardon
- Sabrina Krievins as Teena Simmons
- Jerry Hardin as Deep Throat
- George Touliatos as Dr. Katz
- Tasha Simms as Ellen Reardon
- Janet Hodgkinson as Waitress
- David Kirby as Ted Watkins
- Tina Gilbertson as Donna Watkins
- Christine Upright-Letain as Ms. Wells
- Gordon Tipple as Detective
- Garry Davey as Hunter
- Joe Maffei as Guard#1
- Maria Herrera as Guard#2
- Robert Lewis as Officer