Actually, a good TPK (Total Party Kill) now and then is a learning experience. It also establishes the mood of danger in the fantasy world! PC and whole party kills have been part of the game since day one, and it's all the better for it.
If their band of heroes does not return from the Keep (or wherever), have new adventurers come into town. They hear tales of the previous group and their bravery! The townsfolk may even be sad that they have not seen the heroes return.
Then send the new group into the Keep. Some of the rooms that the previous group cleared have stayed cleared. Others have been repopulated. Any treasure and other swag that the previous group had can be found in a hoard someplace, probably by whatever took the original boys down.
If you've got young'uns just learning the game, now is the perfect time to help them get used to the fact that, while nobody "loses" D&D, characters are not invincible and have to earn their levels. And that survival constitutes a reward!
And if the second group fails... well, the darkness never seems to run out of monsters, so neither should the light run out of heroes. If you're worried about an XP disparity (i.e. that cleared rooms will reduce the XP available for them to level up sufficiently) just hand out a quest card for "Find the Lost Heroes" and give them a big chunk of bonus XP for getting back to the point where the previous group shuffled off the ol' mortal coil.
If their band of heroes does not return from the Keep (or wherever), have new adventurers come into town. They hear tales of the previous group and their bravery! The townsfolk may even be sad that they have not seen the heroes return.
Then send the new group into the Keep. Some of the rooms that the previous group cleared have stayed cleared. Others have been repopulated. Any treasure and other swag that the previous group had can be found in a hoard someplace, probably by whatever took the original boys down.
If you've got young'uns just learning the game, now is the perfect time to help them get used to the fact that, while nobody "loses" D&D, characters are not invincible and have to earn their levels. And that survival constitutes a reward!
And if the second group fails... well, the darkness never seems to run out of monsters, so neither should the light run out of heroes. If you're worried about an XP disparity (i.e. that cleared rooms will reduce the XP available for them to level up sufficiently) just hand out a quest card for "Find the Lost Heroes" and give them a big chunk of bonus XP for getting back to the point where the previous group shuffled off the ol' mortal coil.