Benedict Cumberbatch battled mystery illness, fake crew cut facing Jodie Foster in 'The Mauritanian'

A pivotal scene in "The Mauritanian" places the drama's two biggest stars – Benedict Cumberbatch and Jodie Foster – head to head as opposing lawyers meeting unofficially. It's a legal version of Al Pacino's cop meeting Robert De Niro's robber in "Heat," set in the surreal location of a gift shop near Cuba's notorious Guantanamo Bay Detention Camp.

It was Foster's first scene and first day on the set in Cape Town, South Africa, which effectively stood in for the incongruent Caribbean paradise that surrounds Gitmo. But it was Cumberbatch who struggled as cameras rolled.

"I was getting sick in between takes," Cumberbatch remembers, speaking by phone from London. The 44-year-old "Doctor Strange" star was in the final stages of a terrible mystery malady he picked up on the flight to South Africa.

"I was really ill, I think it was just a really severe flu. But it was really nasty. I hadn't been that ill for quite a long time. Like maybe once in my life. Horrible," he says.

In the pre-COVID-19 era, Cumberbatch was intent on battling forth. "The Mauritanian" (just released on Blu-ray and digital) represented a five-year quest to bring Mohamedou Ould Slahi's remarkable story to the screen.

Cumberbatch was immediately wowed by Slahi’s saga after performing a reading of his 2015 best-selling book, "Guantánamo Diary." The memoir described Slahi's harrowing imprisonment without trial at Guantánamo Bay, during which U.S. officials eventually acknowledged Slahi was tortured to extract an illegal confession to being a 9/11 organizer. After 14 years without a charge, Slahi was allowed to return home to Mauritania in 2016.

"It sort of beggars belief, how Mohamedou bore witness to that period of American history and his part in it with this extraordinary insight," says Cumberbatch, whose production company bought the film rights. "I didn’t know if this would make a great film. But I thought it was an incredibly important story to be part of and at least try to do justice to it."

Intent on producing the film, Cumberbatch slowly, became enamored with the role of American military prosecutor Lt. Col. Stuart Couch during the long process of hammering out the script.

A friend of Couch's from flight training school co-piloted the tragic United Airlines Flight 175 that 9/11 terrorists flew into the South Tower of the World Trade Center. But in a principled stand, Couch quit the prosecution after finding out that Slahi's incriminating statements had been made following 70 days of torture.

Director Kevin Macdonald persistently recruited Cumberbatch for the role. "He comes across as someone who is always one step ahead of you, perfect for this brilliant lawyer figure," the filmmaker says. It paid off, with Cumberbatch agreeing to step into the part just before an offer was made to an American actor.

Couch was one of the last parts cast, with Tahar Rahim portraying Slahi and Foster as crusading attorney Nancy Hollander. (Foster would go on to win a surprise best actress Golden Globe for the performance.)

Cumberbatch dove deep into Couch's daunting North Carolina drawl, rather than a more generic, accessible accent.

"I worked on that for a while," says the actor, who repeats real Couch-isms like "I'd low-crawl through hell in a gasoline suit," lines that were incorporated into the screenplay. He hired two different dialect coaches to help and learned from Couch himself when the devoutly Christian, staunchly Republican immigration lawyer was visiting London.

"(Benedict) was rather nervous about that meeting," says Macdonald, pointing out differing life views. "But (Benedict) called me afterward saying, 'I love this man.' It was a real meeting of minds."

Along with key character insight, and lengthy personal voice recordings for reference, Couch loaned Cumberbatch his Marine Corps gold wings, made by his father, to wear while filming. "It represented a very personal connection to him being a Marine," Cumberbatch says.

Other issues arose in playing the clean-cut military lawyer. Cumberbatch had committed to growing his hair long to play a Montana rancher in Jane Campion's "The Power of the Dog." A prosthetics team concocted a miracle solution, even if it would require hours of makeup each day: Cumberbatch wigged out.

"A bald cap with a mean crew cut, which is quite a thing to do," he says. "Under all of that is this huge lump of hair."

But it was during the flight to South Africa that things got really hairy.

"There were a couple of people who were sick on the flight and there was one guy coughing his lungs out," says Cumberbatch, who grimly jokes that he wasn't sure if he was hit with severe food poisoning, flu or worse in the days right before COVID-19 was identified as a global threat. "I think I might have been patient zero. I was so sick."

As soon as the star arrived, "he immediately got ill, seriously ill for several days," Macdonald says. "But he would turn up every day. And it was sweltering, like 100 degrees in the South African summer. He would go through three hours of hair and makeup for what's basically a bald cap with a wig on it."

Cumberbatch lost his voice for one scene, which the filmmakers were able to re-record later in the editing studio. The actor carried on, seeking approval from Couch himself. Mission accomplished.

"Stuart heard my accent and said I did it ‘spot on,' " Cumberbatch says with pride. "He thinks this is an incredibly important story to tell. Not just his, but the whole story."

This article originally appeared on USA TODAY: Why Benedict Cumberbatch battled to face Jodie Foster in 'Mauritanian'