One of the most striking features of the zombies in Netflix’s new Australian-set Cargo movie is how before the infected finally turn into “Virals,” they dig a hole in the ground and bury their heads. We’ve never seen this bewildering kind of behavior in a zombie before, so what gives? Inverse talked with the film’s co-directors Yolanda Ramke and Ben Howling at Tribeca Film Festival in April, and they helped shed some light on what makes the zombies in Cargo some of the weirdest and most intriguing infected you’ll ever see.

Cargo hit Netflix on May 18, delivering a heartbreaking story about Andy Rose (Martin Freeman) trying to save his baby amidst the zombie apocalypse. Shot in southern Australia, Cargo is as visually stunning as it is tragic as you fear for little baby Rosie’s life with all these zombies shuffling around. So what makes them so interesting?

Full spoilers follow for Cargo.

Andy and his wife Vic early in 'Cargo'.
Andy and his wife Vic early in 'Cargo'.

If you’ve seen the trailer for Cargo, then you know that Andy’s wife Vic is bitten and dies early in the movie, and after she bites Andy, he has t travel across the beautiful landscape looking for somebody that can take care of Rosie after he’s gone. We watch his gradual transformation unfold in tragic fashion. Containment kits distributed en masse by the Australian government offer sparse details, a watch with a timer, and even a handy instrument for assisted suicide purposes.

Once bitten, an infected person has 48 hours before they become a “Viral.” (Ramke and Howling told Inverse that they referred to these zombies as “Virals,” mainly so they wouldn’t have to use “zombie” on-set.) “We wanted to veer away from getting bogged down in science or logic onscreen,” Ramke said. As such, Cargo doesn’t do much to explain where the virus comes from or how it works, but she and Howling still worked out the nature of the virus for behind-the-scenes.

An infected person gradually develops increasing fevers, seizure, and internal bleeding. A nasty green puss oozes from their face until it hardens over their mouth. Eventually, complete insanity occurs, at which point the infected bury their heads in the sand overnight and then burst out looking like they’re in dire need of Chapstick. But by then, not even lip balm can help, because they become mindless Virals.

“With this sort of gooey face,” Rake explained, “we tried to draw from the natural landscape. Tree sap was the reference point for that. The idea is that once that symptom occurs, it hardens over and suffocates the person. That’s their last human moment. When they crack out of that, that’s where the transformation occurred. That drew influence from insect chrysalis.”

'Cargo' zombie movie netflix
Somebody get this lady some Chapstick!

In the later stages, the Virals become sensitive to light, which is why they bury their heads or otherwise seek darkness. (One terrifying scene much later in the movies has a group huddled in a dark tunnel.) That triggers their final chrysalis. Howling specifically referenced cicadas, which burrow into the ground as larvae and mature gradually over a number of years before emerging fully-grown. Some cicada species only emerge every 17 years, but the biological lifecycle remains comparable to a caterpillar weaving a cocoon to become a butterfly.

By aping the biological process of insects, the zombie virus in Cargo therefore becomes so much more naturalistic, even organic. “We wanted this to be a rounded genre film,” Ramke explained. “How do we NOT make this a fantastical virus? What if we made it come out of something more organic?” Much like the Indigenous tribes that are able to thrive in Cargo while Westerners succumb to the virus, Ramke and Howling did that by looking to nature for answers. And the result is a wild success.

Cargo is currently available to stream only on Netflix.

Photos via Netflix