Filmed in 2015, unceremoniously dropped from the release schedule by Sony in 2016 and left sitting on the shelf, forgotten and unloved ever since, Patient Zero, the Matt Smith-starring viral infection thriller – go on, call it Doctor Who and the Zombies of Doom if you must – is finally creeping out to meet a public that probably wasn’t aware it even existed. While it’s not difficult to see why it was felt unsuitable for a theatrical release – bar a few quick flashbacks it’s largely set in one claustrophobic underground location – it’s harder to work out why it’s been kept completely under lock and key for so long as it’s actually a decent spin on the zombie genre whose profligacy is now at the point of driving us all right up the wall.

We’re told, via a tiresome and lazy opening voiceover, about the viral outbreak, the infected, end of the world, people in hiding blah blah blah. Our interest is piqued by the idea that this particular virus is a mutated strain of rabies; this gives our ‘monsters’ a degree of sentience so they’re not just the usual shuffling/running blood-crazed undead of virtually every other film in this hideously oversubscribed genre.

Deep in an underground bunker (the Romero influence is shamelessly exploited) a cluster of civilian, military and scientific survivors are hidden away eking out a fairly miserable existence. Scientist Gina Rose (Dormer) is feverishly working on a vaccine, military boor Knox (Standen) just wants to shoot anything infected that moves, and Morgan (Smith) has been bitten but hasn’t turned into a raging man-monster. Usefully, he can communicate with infected captives and although he can’t make much headway in the group’s quest to find “patient zero”, the first of the infected, he does strike up a potentially-interesting rapport with former teacher Michael (Tucci), who remains urbane and calculating even when consumed by the desire to rip out people’s throats.

Patient Zero doesn’t quite work, and yet it’s not the disaster it might have been due to some interesting ideas which the script can’t quite come to grips with (despite being characterized as semi-intelligent, and the director’s assertion that his creatures are “much sexier” than your traditional undead brain-muncher, the finale descends into the usual brain-munching carnage), a distinct impression that no-one was really sure exactly how the whole thing should play out, and an ending so abrupt it gives new meaning to the expression “oh, is that it?”.

The “patient zero” reveal is a nicely-played twist, and Morgan’s determination to keep his infected wife (Deyn) alive in the hope of finding a cure adds an interesting dramatic dynamic, but the film starts to wobble dangerously as the stakes are raised and it eventually turns into the sort of film we might have hoped it could avoid becoming. But there’s a nice sense of overheated claustrophobia in the bunker setting, the flashback to Tucci’s character’s infection and its consequences is grim stuff, and Matt Smith’s American accent is a baffling thing of joy. Patient Zero clearly belongs nowhere near a big screen but it’s eighty minutes of watchable home entertainment that’s not likely to feel like a complete waste of time.