For 15 years, British games designer Sam Barlow had been toiling away on a number of forgettable titles until, in 2014, he changed tack and became an indie game developer focused on interactive fiction. The following year he released Her Story, an extraordinary, unique experience in which players had to sift through a database of police interview clips in order to solve the mystery of a missing man. It was a stunningly original use of FMV (full motion video), a sub-genre that briefly dominated gaming in the early 1990s before falling out of favour just a few years later. Barlow’s genius was to combine a solidly performed mystery with appropriate interactive mechanics. Two years later, he released Telling Lies, a smart follow-up that proved he was no one-hit wonder.

Immortality is Barlow’s third interactive film and it’s the ne plus ultra of the genre. It focuses on the mysterious disappearance of fictional actor Marissa Marcel (Manon Gage) who starred in three films made in 1968, 1970 and 1999. According to the game’s introduction, none of these films was released but footage from all three has been recently discovered and is presented to the player as part of an interactive cinematic archive. Beginning with a single clip, players use Moviola editing tools to scrub through video sequences, gradually unearthing more footage. This is achieved using a process of match cutting whereby players pause the film and click on actors and objects: select a crucifix in one scene and it might open up a brand new section featuring a cross. This process is deeply satisfying and appropriately visual, and it’s vitally aided by Nainita Desai’s soaring soundtrack.

^{Table read for Ambrosio 1968}

As well as finding material from Marcel’s three films, there’s also plenty of candid behind-the-scenes and documentary footage to explore. The whole thing clocks in at almost ten hours although players will finish the game long before seeing every clip. Crucially, the cast is excellent. While the films themselves are melodramatic, each one is presented in keeping with the era in which it was ‘made’. It’s best to enjoy Immortality knowing no more than that. While this review won’t spoil anything, the next paragraph will expand a little on the mystery.

After spending several hours with Marcel, discovering her various performances and getting to know the actor much more intimately, something startlingly sinister happens, exposing an underlying narrative working against the found footage. Gradually, the player is drawn into this newly unfolding story and there’s impeccable technical mastery behind the way it plays out.

It wouldn’t work at all if the player hadn’t put in hours of preparation, although some might find their patience is stretched before the penny drops. Charlotta Mohlin (Agents Of SHIELD) deserves praise for her extraordinary work in these scenes, alternating between malevolent entity and misunderstood victim. Underpinning it all is a breakout performance from Manon Gage. If she wasn’t utterly convincing as the story’s doomed ingénue then the whole narrative would fall apart. Immortality is a remarkable moment in gaming and it’s hard to imagine how Sam Barlow could ever top it.

Out now on PC and Xbox Series X/S.