The party heads to Thundertree to find Reidoth, the druid. After encountering—and dispatching—a hungry ogre, they make camp near a river for the night. At midnight, while Theren is keeping watch, a pack of goblins sneaks up on the party and attacks. When they are defeated, Theren convinces one of the surviving goblins to reveal the location of Cragmaw Castle. Rather than continuing on to Thundertree, the party heads to the castle directly.
The party invades the castle through a partially collapsed tower, and finds King Graal, a female drow, and some hobgoblin guards. The nameless monk blocks the bugbear and his wolf behind a door while the adventurers handle the hobgoblins, then tosses the door aside to deal with King Graal himself. The drow finally enters the fight, seeing her escape route cut off, but is brought down soon after the last goblin.
Theren and the monk torture the drow to find out that her employer, the Black Spider, had sent her to get Gundren’s map, and wants Wave Echo Cave for himself. When she dies, her adopted form slips away and reveals her to be a doppelganger.
They find Gundren tied and unconscious in King Graal’s chambers and revive him, then find his map to Wave Echo Cave under Graal’s mattress.
On their way out of the castle, they meet some more hobgoblins heading up the hill towards them. One of the hobgoblins demands to know what they’re doing there, but William convinces them to let us pass. The party makes it back to Phandalin with Gundren without incident.
In the morning, Gundren comes down to talk to the party. They head out towards the Sword Mountains, to the entrance to Wave Echo Cave.
In the cave entrance, they find a storehouse full of casks, barrels, mining gear, and the body of a dwarf miner, dead for at least a week. A deep pit lies at the end of the cavern.
“Tharden! No!” Gundren exclaims when he sees the dead dwarf, then looks around, frantically. “Where is Nundro? Nundro, are you there? Maybe he’s still alive…”
The nameless monk goes over to the pit, and finds a rope leading down to a curving tunnel that splits off in two directions. He begins climbing down; the others follow.
After a bit, the passage opens up, leading to a natural cavern where many tunnels intersect. The walls are carved with reliefs showing dwarven miners at work, and the room is filled with skeletons. Sturges attack the party above, putting many of the more frail and fearful among them to flight, but are dealt with quickly.
The party heads back to the cave entrance to rest briefly, where they find Gundren digging a grave for his brother. The monk stays with Gundren to help him dig, while the rest head back into the caverns. An ochre jelly takes Theren by surprise, but he is close enough to the others to call for help, and the jelly is killed.
The monk, having helped Gundren bury Tharden, joins the others in the cavern. Gnawing and scratching sounds lead the party to a stone door, behind which they find three ghouls gorging themselves upon the remains of some dwarves and orcs. The ghouls prove a more difficult foe than the goblins had been, but the adventurers are able to vanquish them regardless, then make camp.