In the new supernatural horror film The Autopsy of Jane Doe (out Dec. 21), actors Brian Cox and Emile Hirsch handle the bulk of the dialog as father-and-son coroners tasked with discovering what killed an unknown woman found by cops at the site of a massacre. But director André Øvredal (Trollhunter) believes the cast member with the hardest job was actress and model Olwen Kenny who portrayed the titular corpse and was required to lie dead still — and naked — for take after take, no matter what was happening around her.

“It was the most grueling role to play, actually,” Øvredal told EW last week at Fantastic Fest in Austin. “She had to lie there on a slab for maybe eight, 10 hours a day for weeks on end. And it was a cold marble table. She didn’t say a word, she just lay there, and was so amazing with everybody, and she made everybody calm. Because it’s kind of an awkward situation, you know, with the nudity, and everything. Her personality made everybody relax.”

So, did Øvredal test the ability of potential corpse-portrayers to remain still during the audition process? “The audition process was more, like, meeting a bunch of potential actresses. She was the very first one I met and she was immediately Jane. I met with a bunch of others, but she was the one from the start. She was really good at shallow breathing because she was all into yoga, and she’s a professional model, so she has control over her body. But, even then, there is a lot of stuff that needs to be done to an image. In a modern movie, in 2016, the audience don’t accept anymore a body that is kind of dead. It needs to be dead! [Laughs] So, there is a lot of CGI.”

You can see the trailer for The Autopsy of Jane Doe, below.