[Warning: This story contains major spoilers from Alien: Romulus.]

For sci-fans of a certain age, it was the surprise of the summer.

That would be the reappearance of Ian Holm as a “synthetic” android in Alien: Romulus, a secret held back from the film’s marketing and even its San Diego Comic-Con panel. As Holm died in 2020 at 88, it was also a major undertaking that required permission from the late actor’s estate and a combination of animatronics, CGI and artificial intelligence to complete the illusion.

The result is the most ambitious effort yet at re-animating a deceased actor for a movie. The last significant attempt — and by most accounts the first — was in 2016’s Rogue One: A Star Wars Story, which featured the CGI-re-created face of Peter Cushing, who died in 1994, reprising his character Grand Moff Tarkin from the original 1977 Star Wars.

Response to that cameo was negative, with many feeling the technology had failed to fool the audience into thinking they were watching a flesh-and-blood human.

A year prior, similar technology was deployed to complete Paul Walker’s work in Furious 7, the actor having been killed in a car accident before filming was completed. Sentimentality over the loss of Walker helped audiences accept the computer-generated trickery.

But the jury is still out on Alien: Romulus‘ own attempt at raising the dead. Some have criticized the ethics involved, calling the move cynical and crass. Slate compared Disney-owned 20th Century Studios to the series’ evil Weyland-Yutani corporation, calling it “a massive conglomerate that puts profit ahead of respect for human lives.”

SlashFilm found the efforts to be an aesthetic failure: “It’s distracting and weird. It never, ever looks real. … The simple truth here is that not only does this look bad, it’s a bad idea all around.”

What is not in dispute, however, is the scope and ambition of the attempt. The role is a sizable one, featured in multiple scenes and delivering significant stretches of dialogue that greatly impact the plot until its shocking fourth act.

In terms of a cinematic advancement, it is a mind-bender: He was one of the most legendary AI characters ever depicted in film, created when AI didn’t exist. Now the human who played him no longer exists, but the AI needed to re-create him does.

This symbiotic idea was hatched by Romulus writer-director Fede Álvarez. In studying the franchise mythology, Álvarez noted that there was a limited supply of synthetic models. (Michael Fassbender played dual, identical models in 2017’s Alien: Covenant, for example.)

Discussions with producer Ridley Scott (who directed 1979’s original Alien, Covenant and 2012’s Prometheus) led to the realization that the series’ first synthetic (though they prefer to be called “artificial persons” or APs), Holm’s Ash, was its most intriguing and worthy of resurrection.

“Ridley was the one who said, ‘Ash was always the best. He needs to make a comeback,’” Álvarez recently told The Hollywood Reporter.

The result is Rook — a look-alike to Ash, who was destroyed in the original film, and a predecessor to the similarly chess-piece-named Bishop, played by Lance Henriksen in 1986’s Aliens. (Romulus is set between the action of Alien and Aliens.)

Unlike Ash, positioned as a villain in the original film, or Bishop, who comes off as an ally, Rook was conceived as a morally ambiguous figure — one whose programmed intentions, good as they may be, might or may not have the best results for humanity. In that way, he stands as a perfect metaphor for the debates currently surrounding the implementation of AI.

“He’s rarely lying to anybody or scheming or trying to con someone into doing something they don’t want to do,” Álvarez explained. “He’s actually pretty straightforward, but that’s the line that was fun to play: ‘Is he going to be more like Ash, or is going to be more like Bishop?’”

As envisioned by Álvarez, Rook works in service of Weyland-Yutani — but instead of using his programming to find ways to weaponize the deadly Xenomorphs, he sees in their DNA a path to perfecting the human race, through a fluid he dubs “the Prometheus fire.” The results are somewhat catastrophic.

Before anything, Holm’s estate would need to sign off on his likeness being re-created for the film. “We went for it with the permission of the family: his widow and all of his kids. We wanted to make sure everybody was on board with the idea of bringing his likeness back,” the director said.

Speaking to Entertainment Weekly, Álvarez revealed a bit more to the backstory. Holm’s wife, the London-based artist Sophie de Stempel, “felt that Ian was given the cold shoulder by Hollywood in the last years of his life, that he would’ve loved to be part of more projects after The Hobbit, but he wasn’t. So she was thrilled about the idea of having him back.” A compensation deal was reached and the estate signed off on his likeness.

It was The Hobbit, in fact, that allowed Rook to happen, as Weta FX, the New Zealand-based company, had a Holm headcast lying around made for Lord of the Rings. (Holm played Bilbo Baggins in several of Peter Jackson’s fantasy epics based on the books of J.R.R. Tolkien.) “That was the only headcast that exists of Ian Holm,” Álvarez said.

A fully animatronic version of Holm — bifurcated and leaking milky fluid after a messy encounter with a Xenomorph — was built by Legacy Effects, the same practical effects company that created The Mandalorian‘s Grogu. That was augmented in post with CG enhancements to animate the nose, eyes and mouth courtesy of Metaphysic, the company behind those viral Tom Cruise deepfakes. “It’s a whole bag of tricks, from 1970s and 1980s technology to technology from yesterday,” said Álvarez.

To re-create Holm’s voice and intonations, actor Daniel Betts performed the dialogue, and the recording was fed through a software called Speecher, which modified Betts’ voice based on Ash dialogue pulled from the original Alien.

De Stempel got her first look at her resurrected husband in June, when Álvarez sent her with some of the Holmes footage. He then got on the phone with her to gauge her reaction. “It was a very, very emotional call,” he told EW. “They lost him not too long ago, and I lost my dad, too, around the same time. So I could relate to their pain and also their excitement to see him back in the movie.” 

Holm’s family saw the final product at the film’s London premiere on Aug. 14 and tells The Hollywood Reporter in a statement, “We loved being there and are pleased that [Fox is] bringing both Alien and lan to another generation.”