Okay so I'm running the KotS adventure module from around May and this Sunday we were at the end of it but something unexpected happened.

Now you'll be wondering what happened. Some would call a catastrophe but I certainly wouldn't. It actually was my adventuring party's favorite session.
The members are: a Dragonborn Rogue, an Elf Fighter, a Human Fighter an Eladrin Warlock and a something(I don't remember the race) Cleric.
Here's what happened:

They were at the second last encounter with the Orcus Underpriest and the vampire spawns e.t.c.
Everything was going well or not that good, the two fighters were at the rear of team and the warlock ended up advancing to the middle of the room.After being attacked by the Human Bersekers he was reduced to half hit points.And then the Rogue on his turn tried to climb down the hole leading to the next room with the rift but as his athletic skills were not that good he fell and was left with 3 hp.Then the Warlock went to help him and fell at minus 0 hp due to the fall. The rogue started desperately to climb back up, reached the 2/3 of the chains and then fell falling to minus 0 hp.Both of them were thrown into the portal by Kalarel as a sacrifice for the Thing in the Portal.The Elf Fighter then retreated to safety but the other Fighter stayed and so didthe cleric.The Cleric seeing that the odds were not that good left but the Fighter died out of stubborness and was also sacrified to the Thing in the Portal.3/5 PCs dead.
After that a caravan was organized going to Fallcrest, the village of Winterhaven left empty and burnt.In Fallcrest the whole town found refuge.

And that's what happened in a 2 and a half hour session but it was a blast. Before this I was planning to run Thunderspire Labyrinth next but now I'm not sure. If you guys could me any suggestions on how to continue (links to H2 or irrelevant ideas) I'd appreciate it.