I blew up the fallen rocks with the Ironhand gnomes' secret stash. I've not had this problem on previous attempts, but now as soon as the dust clears, one of the trapped gnomes rushes out, right through a patch of fire created by the smokepowder explosion and takes damage. This constitutes an attack, and everyone turns hostile and starts fighting without the usual dialogue options with Nere and Brithvar. The only way to stop it happening was for Shadowheart (who was firebolting the explosives from a safe distance) to immediately go turn based and throw a bottle of water onto the fire in exactly the right place.
