In the process of adapting the story, Dawson focused on expanding the mission's crew and decided to lead the story not with Brunel, the group's captain, as in the original story, but rather with senior systems engineer Vincent Campbell. "It's about a chain of events put into play on the very last day of one of the first missions to Mars," summarises Cornwell. "What is unusual is, rather than looking at their arrival on Mars, the story is about a group of people who had been together a long time and looking at the disintegration of the group psychology."
For Vincent, explains director Ruairí Robinson, what happens on the planet plays into the deepest of his fears. "He has a fear of losing himself that becomes manifest in facing something that literally threatens to take over," he says. "That's what first attracted me to the script: to place a character into a situation where they have to face the very thing they're terrified of in the worst way possible."
And it was this notion that attracted actor Liev Schreiber, who found the idea of Vincent's claustrophobia and anxiety immediately appealing. Says Schreiber: "One of the things we started talking about when I became involved was: How do you articulate that claustrophobia? How do you express something as complex as his sort of anxiety?"
All the elements were aligned, he says. "Being trapped in a space station, in close quarters, in spacesuits - all of it contributed to this oppressive, suffocating thing that was really interesting to explore."
In fact, it harked back to some of the most interesting science-fiction horror storytelling on the big screen. The touchpoints within the subgenre were films like Alien, The Invasion of the Bodysnatchers and The Thing. "When we started this there hadn't been a movie in that key in years," says Robinson. "Or certainly not a good one, anyway."
But the influences went beyond science fiction too, he adds. "There are elements of Sergio Leone's Westerns in there - a New Frontiers vibe. And for me, United 93 was a touchstone in terms of the tone of the acting and how to deal with emotion without resorting to cheap tugging at the heartstrings."
