Nearly a year after Grand Theft Auto IV exploded onto the market, the first in a series of long-promised downloadable episodes is finally here. Packing in a surprisingly meaty single-player campaign and a clutch of new multiplayer modes, Grand Theft Auto IV: The Lost and Damned veers sharply away from GTA IV’s immigrant story to focus on Liberty City’s biker underground. Or, more aptly, what’s left of it.

The bikers of The Lost and Damned are the sad dregs of a culture that hasn’t been relevant – in the game or in real life – for at least 30 years. They’re battle-scarred, middle-aged thugs, living on past glories and drug money, and at their center is Johnny Klebitz, the episode’s protagonist. Level-headed but tough, Johnny’s been leading The Lost Motorcycle Club while its real president, Billy Grey, languishes in court-ordered rehab. As the episode opens, Billy’s a free man again, ready to retake the reins of power and utterly shatter the peace Johnny’s worked hard to build.

You can probably already see where this is going to go.

Over the course of the ensuing 23 story missions (which will take around eight to 10 hours to finish, if you charge straight through), Johnny engages in the usual assortment of thefts, assassinations, rescues and all-out gun battles that have become staples of the series. And he’ll usually engage in them while on a motorbike, so it’s a good thing that bikes have been radically retooled to be much more stable, and therefore much more fun.

Most of the missions don’t offer anything that GTA IV’s didn’t (apart from mid-mission checkpoints, which are a godsend), but there are a couple of unique moments. In one mission, you’ll need to switch to a second-person perspective (that of the people chasing you, complete with their dialogue) in order to make sure that your pursuers are following you into an ambush. In another, you’ll have to keep a familiar character under control during a clueless kidnapping attempt, which doesn’t introduce any new gameplay elements but is more simultaneously sad and hilarious than anything else in the episode.

A few of the missions also pit you against ridiculous numbers of enemies, and there’s a good reason for that: as a senior member of the Lost, Johnny rarely does anything without the help of at least one or two of his “brothers.” At first, he’ll tag along with them, riding in formation (with the help of a badge projected on the road) to trigger revealing dialogue. Later, though, he’ll be able to call on two of them – his friends Terry and Clay, who can also sell him guns and bring him free bikes, respectively – to provide backup. Usually this just means they’ll ride alongside you and act as sidekicks (sometimes bringing along a few more members just in case), but sometimes it can change the structure of a mission, as they’ll do things like set up ambushes for pursuing hitmen.

It’s in your interest to call on Clay and Terry as often as possible, not just because of their oafish help, but also because they’ll gain experience and improve their fighting skills the more they help you. The disposable Lost members they bring along will improve, too, but they also tend to die a lot, so it really doesn’t matter.

The action is strung together by a story that parallels the events of GTA IV, often intersecting with Niko’s narrative. Sharp-eyed players might remember Johnny from his brief appearances during a couple of key missions in GTA IV, and it’s interesting (if weirdly unnerving) to see those familiar events unfold from a different perspective. But this is Johnny’s story, not Niko’s, and so the diamonds and mob politics take a backseat to Johnny’s more personal struggles with his friends and with his own antiquated, often-broken code of brotherhood and loyalty.