Josh Hartnett on his role as a tech guru plagued by his own creation in The Fear Index

Multiple Teen Choice and MTV Movie Award nominee Josh Hartnett (Wrath of Man, Pearl Harbour) stars as Dr Alex Hoffman, a tech genius who faces the worst 24 hours of his life when he finds himself at the centre of a plot to destroy the world's financial markets in the Sky Original psychological thriller The Fear Index.

Based on the best-selling novel by Robert Harris, about the 2010 Flash Crash, the four-part miniseries also stars Senegalese actress Aïssa Maïga (The Boy Who Harnessed the Wind, The African Doctor), Arsher Ali (Avenue Five, Four Lions), and Leila Farzad (I Hate Suzie, Avenue Five).

The Guardian says, “It’s solid, satisfying stuff… given a remarkable lift by Hartnett, who invests Hoffman with a palpable, credible and increasingly corrosive fearfulness from the off,” adding, “Fear of losing your mind, fear of the unknown, fear of the robots taking over our lives, fear of failure and of danger and humanity’s fearsomely predictable responses to it all entwine nicely, somewhere around the viewers’ throats.”

Watch the trailer for The Fear Index

Read on for more about The Fear Index, and what Hartnett found most interesting about his role.

What drew you to The Fear Index?

I loved Robert Harris’s book. He is so good at this genre. Also, the producers, Left Bank, are responsible for The Crown, which I’m a huge fan of. They’re very much at the top of their game. So when I was approached by them, I thought it would be great to be part of this, and I wasn’t disappointed. I’m delighted to have been involved in this terrific production.

What makes Robert such a great writer?

He is very prescient. His novel of The Fear Index was written a decade ago, but the concept is still very current. It’s still something we’re all very much talking about. It doesn’t feel dated at all.

Tell us more.

Robert has a very keen grasp of the human condition, and he also knows how to create a really intriguing story. He possesses the perfect balance – he writes gripping blockbusters, but he also has a very deep understanding of people. That combination is getting rarer and rarer. He really hits the sweet spot.

The underlying idea of the story is pretty terrifying, isn’t it?

Definitely. It’s scary to think that we’re creating things beyond our understanding and that no one person has the knowledge that these machines have. The danger is that they become ungovernable. That’s what makes this thriller so dramatic.

What is the story based on?

It’s based on Frankenstein, and it works brilliantly. Alex fits the model of Dr Frankenstein very well. A lot of scientists and tech guys are uncontrollable. This story shows that we’re at their mercy and how fallible that process can be.

How would you describe Alex?

At this point, he is living in a world that he doesn’t understand. His friend Hugo has hired himself to deal with the day-to-day things in the company that Alex is not interested in pursuing. Alex is driven only by the concept.

More than anything, he is interested in using the world of finance to create the series of data points, rather than making money. He is more interested in science than finance. The problem is, the more knowledge his machine acquires, the more sentient it becomes and the more danger it poses.

How would you characterise Alex’s relationship with Gabby?

She is the first big love of his life and his protector. She understands the ways of the world much better than he does. Alex only sees the upside, but Gabby takes everything that is happening with a grain of salt. She is also able to understand the shadiness of Hugo.

A guy like Alex, who was a young prodigy, has spent his life with people who are not his peers, so his social skills are negligible. But Gabby has those skills in spades, and he finds that very alluring. He hasn’t had to take care of himself before, and she’s helping him to do that now.

Can you outline Alex’s friendship with Hugo?

Hugo is everything Alex would like to be in terms of his ability to charm people and navigate the world. Hugo is very important in helping Alex achieve his ends. The problem is, Hugo has no scruples. He will throw anyone under the bus, in order to get his way. Alex doesn’t see that coming. Money does strange things to all of us!

Why is fear such a potent force?

It can be the most useful emotion when you’re on your own in the middle of a hostile environment. It can be very powerful influence for good. But it can take you down the wrong path and lead very quickly to panic. That’s when you lose your bearings.

Does The Fear Index show that science is risky?

Science can be dangerous if you let it run unchecked. So this drama is a love letter to the peer review process. You always need someone else to test your theories. If other people vet them, science is the best implement we have. It’s a very powerful tool, if it’s used in the right way.

There was a great sense of camaraderie between you four lead actors in The Fear Index, wasn’t there?

Absolutely. We got on so well. We were an amazingly diverse group. Arsher is an extraordinarily thoughtful person. He is a very loyal friend who is so much fun. He was lovely to be around. Grégory and Leila were wonderful, too. She was the “glue guy” who kept us all together. She is one of the most delightful people you could ever meet. It was such a heavy shoot, and we filmed a lot of pages every day. I was there for every scene and did not have much time to recover. So when we did hang out, we took the opportunity to really bond. If I had a night off, I’d say, “let’s go and have a few drinks together and chat about how tired we are!”

Editor's note: This interview was recorded before the SAG-AFTRA strike that began in July 2023.