The generator stopped and the lights went off!
Of all the "OH SNAP!" moments in Left 4 Dead, this one was by far the best. I literally got chills and cackled in glee. We ran out together to to defeat the tank (barely), fight off the horde (it cost us poor Bill), and restart the generator (took four tries). I stopped to replenish my ammo while my son ran ahead. A hunter took me down, and as he ran back to save me, the vehicle finally lowered and it was time to go. "Go on, leave me, go, go!" I cried, and as I died, I saw him shoving zombies aside, and crawling into the van. Everything looked fine, but another Tank showed up and pounded him dead. So close was the death that we actually saw the van pull out, and for a second thought that we had succeeded.
Alas, it was not to be. We found ourselves at the beginning of the level once more. As quickly as we could, we moved through to the finale. This time, we spaced the propane tanks out more, and there were a couple gas cans we used to great effect. I switched to the auto shotgun, which seemed to work a bit better for me. When the lights went out again, we were totally prepared. The Tank came to us, but I lit him up with a molotov and he quickly fell. My son restarted the generator and I covered his back. This second attempt was quite successful, and we were both tucked safely in the van as it drove off. (Sorry Louis!)
We swapped high fives and fist bumps to celebrate. As the stats rolled by, we talked trash to each other. Sure, I took more damage, but I had 4% more headshots than he did; you know, this sort of thing. The total time, with the two restarts, was 1 hour and 5 minutes. For those 65 minutes, the two of us were the kings of co-op, buddies once again. It was a great feeling. I told him about this new mode called Survival, like Horde mode, sort of, that I wanted to try out. He looked at his watch, and told me he had a phone call to make. Sure, I said, maybe tomorrow we'll play again. He walked off to his room, and I debated whether I should maybe look up a friend or three online. I decided not to; the evening had been special, pure, just about perfect. I didn't want to mess that up. I wondered if he felt even half as good as I did. I figured he just did it to get the old man off his back for a bit.
When he came to tell me good night (no kisses, of course, not since he was twelve or so), he told me we needed to get some of those cool Left 4 Dead movie posters, because they are awesome. I nodded, agreed, and wished him good night. Maybe, just maybe, he enjoyed our time together as well. Perhaps teenagers aren't as bad as zombies, after all.