Streets in Cardiff came to a standstill following a new zombie craze set to sweep the rest of the UK, including a Yorkshire city.
The cross-city chase game, 2.8 Hours Later, sees players immersed into a film-like story where actors playing the undead are out to get them.
It is set to come to Sheffield later in the year.
As well as having to outwit and flee the hordes of zombies en-route, participants also get to interact with several characters along the way and avoid getting infected.
Around 500 people in the Welsh capital got in on the act across six locations, including Cardiff City’s football stadium, a primary school and an eerily deserted recycling centre over-run with bloodthirsty monsters.
The aim of the game, which takes inspiration from horror films such as Night of the Living Dead and 28 Days Later, is to find clues at mysterious locations in order to reach safety in the asylum zone.
As well as being wary of zombies – in full costume and make-up – players also have to be aware of police and other government authorities trying to quarantine civilians in order to stem the flow of infection.
The aim of the mission is for players to make it back to the asylum, with their tasks completed and without being “infected” with invisible ink.
A UV light is used to scan for ink marks and all players infected were turned in to zombies ahead of the game’s afterparty.
The 2.8 Hours Later series, developed by game designers Slingshot, is now in its fifth year and has seen more than 60,000 take part to date.
Simon Evans, who co-founded 2.8 Hours Later with his business partner Simon Johnson, said: “It has been incredible to see players become totally immersed in the narrative, and they seemed to love the adrenaline kick they got from playing the game.
“Tickets sold out so fast that we had to add an extra date.”