If we'd noticed the rumble sooner, we might have made it. We were sheltering in a mostly-intact bungalow, the only building with working lights on that particular stretch of rain-lashed, slowly flooding street.
One of the occasional storm flurries had hit, the rain so heavy that we couldn't see more then a few feet ahead, and so noisy we couldn't hear the shrieks of the fallen.
We'd taken shelter to wait it out. Then somebody said, "Hey, my pad's rumbling." And then a massive, Hulk-style Tank zombie smashed through the wall, its crashing approach and signature music having been completely obscured by the storm. And then we died.
This is one of many, many moments where Left 4 Dead 2 goes that bit further than the original, adding a new and often fatal twist to the four humans vs. infinite undead setup of the first game.
While the structure remains unchanged - you and three other survivors, played by friends or bots, carve through hundreds of sprinting undead between a series of safe-room checkpoints, ending in a dramatic and drawn-out set-piece battle - and the world is recognisably the same, it's a much more dynamic, interactive, and suicidally dangerous place.
There are more weapons, more zombies, more variety in the tasks, more distractions and crucially, a massive new range of panicked, almost-heroic disasters.
Each campaign has a unique series of events, locations and types of zombie that demand a slightly different style of play. Dead Center starts crawling along an open hotel balcony, hoping you aren't going to get punched out into the void, before descending into a smoke-filled inferno, out into abandoned streets before a finale spent hunting down fuel cans in a shopping mall atrium.
Dark Rain, scene of the previously mentioned Tank, goes from small village to abandoned factory to claustrophobic cornfield, then all the way back again while the level fills with movement-slowing rainwater.
If the first game felt like a single movie, this feels like a particularly full-on TV series: a sort of 24 Hours Later. There are still places where you stand your ground and fight, but they're outnumbered by those that force you to keep moving, because the zombie hordes won't let up until you complete that challenge.
You're running back with a case of cola for a gun shop owner, following a rollercoaster from start to finish, grabbing fuel cans to top up your escape vehicle... there's never a moment to stop and ponder, you've just got to keep fighting on.
But as ever, do it together. The first game funnelled you down cosy, hemmed-in paths that made it fairly straightforward to work out where the next brain-hungry mob was going to come from.
The sequel opens things up, leading you into mazes of fairground stalls or crypts (some of which the Director has the limited ability to rearrange), or leaving you to strike out across an open swamp or pitch-dark sewer. It's harder to work out where you're supposed to be going, and easier to find an unexpected zombie chewing on your shoulderblades because they've got more angles of attack. Stay together out there, people.
But not too close, because the rarer, more powerful Special Infected are extremely good at splitting you up. The old guard all return: the Hunter leaps and pins you down, the Tank throws you at cars and vice versa, the Smoker drags you off with its tongue, and the Boomer sprays you with vision-obscuring, zombie-attracting bile - although the latter is also now available in female 'Boomette' form, which looks like a bloated, green-tinted Jerry Springer guest.