About halfway through the your trip to Phandalin, you were ambushed by some goblins who you quickly dismantled. After realizing the goblins had seemingly kidnapped your employer(Gundren Rockseeker), you followed the trail to a cave.
Through some bullshit uses of disguise kits you swindled the goblins out of all their money, then murdered them all. In that order. Then the big bossgoblin fell off a bridge while attempting to blow that popsicle stand and broke his skull, dying hard.
Mysteriously, all the stolen loot seemed to burst into flames of its own accord after Randall left the room.
After reviving the man who had been tied up in the cave you studiously ignored his exposition monologue. He told you that Gundren Rockseeker had been taken to a place called Cragmaw Castle by the order of someone called the Black Spider. You then spent the night in a cave full of corpses and realized that you had leveled up.