BioWare was always going to return to the Shadow Broker; the mysterious information trader's existence has been dangled in front of us for long enough for everyone to know that we would eventually get to unwind that proverbial ball of yarn. But what seemed less certain was whether, after nine months of unremarkable and lacklustre DLC, this addition to BioWare's growing Mass Effect universe would actually be any good.

It is. Thankfully, BioWare has finally delivered on some meaty content that makes going to the effort of reacclimatising yourself to the corridors of Illium completely worth it. The first challenge: check your e-mail. Then remember where Liara's office is.

Everything goes a bit pear shaped after all that, with Shepherd and his gang wrapped up in Liara's ongoing quest to locate that pesky Shadow Broker. New information has arrived about his location, and before you can say how's your Krogan you're all off gallivanting around the universe, shooting people on the other side of some long corridors and getting involved in an exciting hovercar chase.

The quest, which will take a couple of hours to see through, is typical Mass Effect fare and includes, amongst other things, a fistfight, two decent boss battles and a zero-gravity rummage across a rickety spaceship exterior. As always you're mostly being funnelled down long, thin corridors with plenty of chest-high objects for cover, though the game (again, as always) does a good job of hiding this with an abundance of excellent aesthetic touches.

Taken on these elements alone, Lair of the Shadow Broker would be a decent but unremarkable excursion. BioWare's most significant success with the package is that it has constructed a side-story that doesn't feel disconnected from the main game. Instead, the DLC functions as a perfect blend of some pertinent sub-plots that effortlessly tie together story threads from both games. Hardly an easy feat: just look at some of the other DLC packs for proof.

Not to mention the appeal of getting (some of) the old team back together. Liara accompanies you for much of the quest, although her time with the gang is fleeting and she cannot be recruited as a permanent member. Still, there's a certain joy derived from the nostalgic twangs as you trump around with Liara and Garrus in tow.

The dialogue, too, is absolutely spot-on. Filled with huge chunks of new conversation, Lair of the Shadow Broker puts Shepard into full-on ass-kicker mode and has him (or her, if you're that way inclined) mostly stomping around with comedy one-liners and sweet putdowns. One exchange, as Shepard and Liara are busy dodging bullets, debates why mercenaries always approach in dribs and drabs from various directions instead of attacking all at once: hats off to BioWare for turning a common conceit of game design (of which Mass Effect is as guilty as anything else) into an effective joke.

More important, at least for anyone yet to reach the endgame, are the various bonuses offered to you by completing the Shadow Broker's main quest. You're given access to some fancy computer terminals, and for pocket change you can have mineral-rich planets lit up on your map. Then there's the ability to dispatch teams of mercenaries out to faff about and occasionally bring back fistfuls of credits, giving you the option to perpetually cycle easy boosts to your economy and minerals.

On top of that, and perhaps more pertinent for fans of the universe's rich backstory, is a collection of dossiers that serve to flesh out the history of the game's supporting cast. Highlights include Miranda's online dating conversations, Legion's gaming records and the title of Jacob's most viewed porn movie. Which he watches while working out, obviously.

Without wanting to delve any deeper into potential spoiler territory, Lair of the Shadow Broker also takes a turn in a direction that can't help but affect Mass Effect 3. The predicable twist can be seen coming a mile off, but it's an undeniably satisfying way to advance the narrative, and will indubitably make Mass Effect 3 all the sweeter. You can't exactly say that about the Overlord pack.

But fans unprepared to shell out any money will, other than missing out, be happy to know that this doesn't put a neat and tidy bow on the whole Shadow Broker storyline. It plays with the characters, teases a few conclusions and ultimately leaves you left wanting more. It might not be too cheap at 800 Microsoft Points, but it's an exciting and cinematic ride while it lasts.