You and Gundren lock eyes for a moment, and in that split second you decide this is not worth it anymore and leave. After sneaking back out of the cave and making your way to Phandalin you go back to your daily life.

Many months go by and not a day goes by that you think, "What have I done???" Because of your actions the majority of the Swordcoast has been taken over by the Black Spider Cultists. Their mission is to bring the horrors of the Underdark to the surface. Seems as though someone knows how to finish quests around here.