Half-Life 2: Episode Two

We then meet Dr. Magnusson, an old colleague of Gordon's from Black Mesa. He's haughty and assured, and explains that the data packet Alyx retrieved from the Citadel in Episode One is just what he needs. And just what the Combine don't want the resistance to have. In fact, it's "the lynchpin to all of their plans". "Somewhere in that sequence, they would have had to establish a connection with the far-side." Magnusson and co. are busily preparing a satellite, and need that data. "If I'm right about this, and I've no reason to doubt myself," Magnusson pompously intones, "you are carrying the very code Dr. Mossman had hoped to recover." Before anyone can say much more though, the transmission breaks down, and a Combine chopper zooms into view through the windows. It's clear what has to happen: Gordon and Alyx have to head north, to White Forest, and deliver the data packet to the resistance. Game on.

Soon it becomes clear that the Combine know what's going on. In a separate section, we're shown a train of Combine vehicles and units moving over a bridge, as you watch from a shack with Alyx and an unnamed Vortigaunt. There's a Combine Advisor (remember the slug-like creature that produced those psychosomatic energy flashes when you were working through the Citadel in Episode One?) being moved, as well as lots of the choppers, Striders and grunts. "They move north with great purpose," our new Vortigaunt friend grimly acknowledges.

So we have to get a move on. Fortunately we've got a new vehicle to help with that. Episode One was completely devoid of vehicles, despite quite a few in Half-Life 2 itself. "One of the goals for Episode Two is to get players out of City 17 and into the wilderness, and to do some more freeform, less linear gameplay elements, and we thought it would be cool to give players a sweet ride to drive around," Speyrer explains. "In service of that, since we wanted Alyx to be with you throughout, we gave her the ability to ride in the car as a passenger. She can get in and out whenever you do, and she can fight from inside the car." This she does with aplomb as we rocket around the hills and through the trees of the outlying areas of City 17; as a zombie grabs onto the front of the car and we twist and turn, powerless to fight it, Alyx raises a foot and smacks it square in its decaying chops, sending it under the wheels. "We've also enhanced Alyx's combat AI, so you'll see her doing smart things," says Speyrer. "You'll see her hide behind counters and shoot over the top, or take cover next to a window and blindfire when she's pinned down." Still no word on an encore hug though.

But there's no time to lament that because the next section we play quickly changes tack - and our focus - and shifts it to the game's biggest new addition, the Hunter. A relative of the Strider (they're in the same "synth family"), the Hunter's another tripod walker. Artist Ted Backman is said to have drawn inspiration from beetles and crustaceans for the design, while Speyrer, who worked on the AI, says that "behaviourally it's like a predatory dinosaur, sort of like a velociraptor, but with guns". Which hurt. Explosive darts fire from its, I dunno, beak, and they complicate cover-and-fire tactics because they stick in the ground and explode after a few seconds. You have to fight their mobility with your own, and that's no easy thing, because they take what feels like a dozen shotgun rounds to go down, and they work in packs. As I tackle one in a rundown building, the other exits through a hole in the roof, circles round and engages me from behind. I die a couple of times trying to take them down, and then go outside and come up against two more.

This section also throws up a puzzle that involves swapping round electrical wires of differing lengths using the gravity gun, and it brings to mind the relative lack of puzzles in Episode One. Is that going to change? "Episode Two has a little more puzzle density, but they're also much more varied," Gautam Babbar says. Speyrer elaborates, saying we'll see "more set-piece maps, where the whole area is built around this one central theme, maybe a large-scale puzzle". Valve's marketing director Doug Lombardi, keen to set expectations, grins and adds: "I think it's fair to say that there's at least one puzzle in Episode Two that's on the same scale as the crane puzzle in the original Half-Life 2."

Expect combat to puzzle as well. Following a blistering ride in the muscle car, dodging exploding orbs dropped by a chopper, the whirling bird turns on you and a pocket of resistance fighters caught in the midst of huge metal containers with no way out, and - more significantly - no rocket launcher to aid you. What to do? We won't spoil it, but you'll kick yourself when it clicks. And for the record, it doesn't involve the Strider Buster - a Magnusson invention that clamps onto the underside of Striders allowing you to target it for an easier takedown. In fact, we're not even shown the Strider Buster, or Dog's brilliant-looking showdown with one of Half-Life 2's most menacing enemies, although we're assured that the latter "does happen".