While everyone currently knows Sony’s Bend Studios for Days Gone ’s post apocalyptic carnage, it also has another name you might recognise: Syphon Filter. It’s an old PS1 classic created back when the studio was still called 989 Studios. It’s not a coincidence there's a trophy called ‘Lend Me Your Ears’ that you earn for collecting, wait for it… 989 Freaker ear bounties.

The Syphon Filter series shipped three games on PS1 and a further three on PSP between 1999 and 2007. It was a world of action movie spies fighting international terrorism from one set piece to the next, with more than a hint of Mission Impossible to its stealthily global adventure. While it’s largely a footnote in PlayStation history these days, it hasn’t stopped older fans hoping for a sequel.

The thing is that, while not everyone will realise it (or like it), Days Gone may well be, appropriately enough, a stealth Syphon Filter sequel according to a series of Easter eggs and references that can be located in the game. But before we get to that we need to recap what Syphon Filter actually was. The series starred Gabe Logan, an agent for the International Presidential Consulting Agency or IPCA. It was an anti-terrorist organization that for most of the six games jetted around the world trying to stop bioterrorism, mostly using the genetically targeted syphon filter virus that gave the series its name.

Days Gone’s world of mutated, feral Freakers might not immediately sound very similar but even early doors there are hints and suggestions that tease at some connections. Later stage, there’s full on documentation that feels like a basically blatant confirmation that it all takes place in the same world as Syphon Filter, and the Freaker outbreak could very well be the result of something Gabe Logan and his team encountered. If Syphon Filter is a game about intergovernmental agencies trying to stop dangerous diseases ending mankind then Days Gone could very well be ‘Syphon Filter 7: Didn’t Stop It This Time.’

The first clues appear when NERO arrive on the scene. The National Emergency Response Organization is the remains of a Days Gone’s version of FEMA who, having failed to contain the virus appear to have retreated from site, only appearing as yellow suited research teams choppering into investigate the outbreak. It very much feels like a call back to the original Syphon Filter opening.

Not to mention that NERO troops look a lot like the Chemical and Biological Defense Command, CBDC, that helped Gabe in Syphon Filter.

So far, it’s just a nice nod to the old studio’s games. Then, during a mission to follow NERO, Days Gone hero Deacon hears this exchange between a NERO scientist and soldiers:

“This virus is on a mission. The Freaks are what they are because the virus wants them this way.

“What are you saying?”

“I’m saying, Jesus, what am I saying…?”

“Terrorism? You’re saying this was deliberate?”

“I don’t know.”

That’s quite the hint to drop; that the Freak virus was man made. The in-game field note you unlock for overhearing that audio clip even states “speculation that the virus is bioengineered”. The developer of six games about weaponised viruses aren’t going to slip in something like that without certain people raising an eyebrow.

However, it doesn’t take long for the game to basically out and out confirm that this is Syphon Filter’s world, with a report you can find in the Cloverdale laboratory where Sarah, Deacons wife used to work.

For those not up on their Syphon Filter lore then it names just about everything important to the series. Gabe, along with his partners Lian Xing, Teresa Lipan and Lawrence Mujari. The location of several Syphon Filter attacks, company fronts used by various terrorist organizations like Kemsynth and PharmaCom Industries. It’s less an Easter egg and more a certificate of authenticity: The Syphon Filter virus, and so that game’s characters and events, exist in Days Gone. To really salt the post-apocalyptic wound, Sarah discovers part of her research was used to create the Freaker virus… for reasons. We’ll skip past the bit where she’s a botanist who has you fetching lavender for burn medicine and how that links to weaponised DNA altering viruses.

The final pin in the proof sheet that this is basically a Syphon Filter game appears after you’ve finished Days Gone. All throughout the game, you’ve been able to pick up IPCA tech from the bodies of NERO scientists without ever knowing what for. Once the game ends you’re able to get a crafting recipe to use it with. Collect all 18 pieces of Days Gone IPCA tech and you can make an IPCA stun gun. But it's not just any stun gun, oh no – this is Gabe Logan’s taser from Syphon Filter. It famously initially electrocutes enemies and then, eventually, sets them on fire if you ‘forget’ to let go of the button.

It’s even got Gabe Logan’s initials on it, just to really drum the connection home:

Short of actually meeting Gabe in person, Days Gone makes it pretty hard not to imagine this is the same world Logan and his team used to protect. Of course, what that means for a more traditional sequel to the Syphon Filter series isn’t as obvious. Somehow a post-apocalyptic espionage thriller doesn’t quite sound right. Although it does sound kind of cool...