Alien: Romulus’ connection with Prometheus explained

Alien: Romulus is out now in theaters worldwide, much to the joy of many who had it listed as one of their most anticipated upcoming movies of the year. Set in-between the events of Ridley Scott’s Alien and James Cameron’s Aliens (two of the best alien movies ever made), we follow a group of young scavengers as they face some familiar foes in what they believed to be an abandoned space station.

This is an Alien movie so to an extent you somewhat know what to expect, but Romulus also has some surprises in store including some various connections to the very divisive 2012 prequel Prometheus – especially with the film’s jaw-dropping ending... Let’s dive into it!

Huge spoilers lie ahead for Alien: Romulus. And if you haven’t seen the film already, check out our Alien: Romulus review for our verdict as well as our guide to the best movies and shows to watch before Alien: Romulus if you want to prepare yourself before heading to the theater.

What is the compound and how does it connect to Prometheus?

(Image credit: 20th Century Studios)

It’s discovered that the abandoned space station holds secrets with its synthetic Science Officer Rook (portrayed by the late Ian Holm who famously played Ash in the original Alien film) revealing that the team there have been analyzing xenomorph DNA, discovering a gene they think will help create “the perfect organism”. 

With humanity struggling to survive in their various space colonies, Weyland-Yutani have created the ‘Compound Z-01’ using what they extracted from the xenomorph. Describing this as a “divine gift to humanity”, clearly the plan is to use this on people, with Rook urging our protagonists to take it back to the company for further development.

If you think this sounds familiar you would be right – in fact, we even get an explicit reference to the film where we have seen this compound before as Rook calls the discovery the “Prometheus file”.

As you may recall, 2012’s prequel Prometheus also featured something known as ‘Chemical A0-3959X.91 – 15’ and ‘Agent A0-3959X.91 – 15’, or more commonly as the ‘black goo’. Developed by the alien species the Engineers, this pathogen aimed to create life-forms and be used as a biological weapon. It’s safe to say that this is the same substance to what is used in the compound we see in Alien: Romulus being reverse engineered in the hope of advancing humanity – and to make this even clearer, we are treated to a snippet from the Prometheus score too.

Notably in Alien: Covenant we were introduced to ‘Steatite Ampules’, which are essentially urns designed to store the black goo and maintain a controlled environment for it. During the sequence in Alien: Romulus where Rook tells us about the compound, we see a hologram of one of these.

What is ‘The Offspring’?

‘The Offspring’ is the name given to the gnarly creature Kay (Isabela Merced) gives birth to in the final act of the movie. Early on in the film we learnt that the young space scavenger is pregnant, which for any Alien fan would raise alarm bells, as this never ends well in the franchise. And whilst the baby at that time was certainly human, that changes when a desperate Kay, clinging on for survival after facing the xenomorphs, injects herself with the compound that Rain (Cailee Spaeny) handed her.

Speeding up the pregnancy she soon gives birth on the ship to a baby that is encased in an egg, filled with acid blood. Falling through the floor to the cargo hold below, the baby breaks free from the egg and quickly grows into something that is listed in the credits as ‘The Offspring’. Essentially a human-xenomorph hybrid, this being is played by actor, and former college basketball player Robert Bobroczkyi, who stands at an incredible 7 foot 5 inches tall, giving the monster quite some height.

Complete with a skeletal body, a sharp tail, and a second inner jaw just like a xenomorph, it really is quite something – and absolutely terrifying. Intriguingly, its face also resembles that of an Engineer from Prometheus, which tracks given The Offspring is partly born from the black goo featured in that movie.

Thankfully Rain takes it on in battle and defeats it, putting an end to the nightmare. However, given that other vials of the compound are in a storage unit on the ship and Weyland-Yutani knows of their existence, maybe we will see beings like The Offspring again in the future, especially if we get a potential Alien: Romulus sequel.

Alien: Romulus is out in theaters worldwide now. For more sci-fi action, here’s how to watch the Alien movies in order, everything we know so far about the upcoming Alien TV series, and our favorite Alien facts that will blow your mind.