Shellshock 2 is a game with admirable intentions that initially impresses with both its subject matter and the execution of its grimy locations. And then opens itself up for cheap gags.

It’s a promising beginning. A dark, filthy field hospital, a general with a penchant for frank language, and screaming victims of unknown attacks. Moving through, you get snatches of backstory before the game’s first horror moment. Pandemonium breaks out as the building’s locked down and becomes a quarantine zone, while you try escape through a Vietnamese attack. There are some effective COD4-like scripted moments, and the game proper begins.

It establishes its oppressive atmosphere well, and the helpless soldiers and blood-smeared walls of this first location stay with you as you begin moving through the more traditional shooter fare of its subsequent levels. There’s still the odd surprise, however, and not in an entirely good way. A scripted moment triggers at the end of one section as a grenade blast knocks your character backwards. He begins blacking out, brief glimpses of the carnage can be seen as his eyes flicker shut, and another soldier can be seen trying to drag victims to safety. All goes silent.

After a pause, you wake up next to a pair of shapely ankles. Obviously intrigued, the camera pans up… and up, and up, taking in the full glory of a finely sculpted, tanned pair of legs, topped off with some tiny camo hotpants. Amid the blood, grime and broken men, you could be forgiven for a little surprise when first meeting the sassy Serena – she’s even twisted her army shirt into some sort of bra. Then, she asks if you “wanna touch” and insists you’re going to show those other boys how a “real man” looks after a woman. And all the hard work up to that point goes out of the window.

Shellshock 2 is trying to create a world of dread, of swift and shocking violence in cramped locations and chaotic firefights that leave few alive, but it sacrifices that tone for a moment that adds little to the experience. Further on from this, Serena is downed by one of the raging zombies that begin to infest the levels. Whether this means that the entire set-up is some kind of elaborate parody, or (more likely) heralds her return as some kind of sexy zombie hardly seems to matter.

Hopefully these moments are isolated hiccups rather than a general wavering of atmosphere and tone, and in the context of the first few levels, playing it for laughs is something Shellshock 2 should avoid. The basic gunplay is solid enough, and there’s promise in the tale of a drug-fuelled US military trying to cover its tracks in Vietnam. If the hotpants are kept in their drawer, this could be a welcome surprise in the fallow post-Christmas period.