Step 1
Chat with Sigmund.
Talk to Hans, Cook, Bob and Father Aereck.
Talk with Sigmund.

Items needed: Bring all required and recommended items.

Make your way to the second floor of Lumbridge castle, and talk to Sigmund. Ask if he has any quests for you. He will ask you to go around and ask people if they knew what happened in the cellar.

If you talk to the men and women around Lumbridge Castle they will tell you that they don't know what happened. Talk to Hans, Cook, Bob and Father Aereck and one of them will tell you that he saw something.

Go back to Sigmund and tell him that one of them said he saw something, Sigmund will then tell you to tell the Duke of this. Once you talk to him, a conversation will start between the Duke and his advisor, eventually the Duke will give you permission to investigate.

Step 2
Crawl through the tunnel.
Pick up the 'brooch'.
Talk with the Duke. Show Reldo the brooch.
Talk with a general.
Pickpocket Sigmund's key, and unlock the chest.

Make your way down to the cellars of Lumbridge, you will find a blocked off tunnel east of the ladder. Use your pickaxe on it and you will create a hole, make sure you have a lit lantern, and crawl through it.

At the entrance of the tunnel you will find a brooch, pick it up. Proceed further south to a "dead end" and you will find another obstruction in the wall. Clear it so that if you should make a mistake in the coming maze, you will be swept away to the Lumbridge slayer dungeon just south. By clearing the hole, you only need to walk north to get back to the start of the maze. The obstruction cannot be cleared from the slayer dungeon side.

Go and talk to the Duke of Lumbridge and say you dug through the rubble. Sigmund and the Duke will talk for a bit, then the Duke will tell you to go talk to the librarian in Varrock (Reldo).

Go to Varrock and talk to Reldo, located in the palace north of Varrock square. Talk to him and show him the brooch and you will tell him that you found it in the caves. Reldo will then say he has a book written about goblins and that it's in the west part of the library, search the bookcases there and you will get a goblin symbol book.

Read the book and you will discover that the symbols there are similar to the ones on the brooch. Head off to the goblin village north of Falador and east of Taverley (Picture) and talk to one of the goblin generals there. Choose the options in this order:

1. Have you ever heard of the Dorgeshuun?
2. It doesn't really matter
3. Well either way they refused to fight
4. Well I found a brooch underground...
5. Well why not show me both greetings?

The goblin generals will then show you how to do the Goblin Victory Dance and the Goblin Bow (Picture).

Go back to Lumbridge and pickpocket Sigmund for a small key (Level 13 Thieving is required) then go and use the key with the chest in the room south of the Duke's room. You will get a full set of H.A.M. robes. You will then discover that Sigmund is in the Human Against Monsters cult! Inform the Duke about Sigmund.

Step 3
Reach the goblin caves in the maze.
Do a goblin bow for Mistag.
Talk to the Duke Of Lumbridge.
Go to the H.A.M Hideout, get Duke's silverware.
Give Mistag the peace treaty.

Go into the cellar, making sure you have a pickaxe, a lit lantern, and a tinderbox. Food is also recommended, because you could get hit by falling rocks if you go the wrong way. Before wandering into the maze, go south to a weak wall and clear the hole. Once inside the maze, watch out for traps that will send you into the Lumbridge slayer dungeon. If you end up there, you can head north and crawl through the formerly blocked off tunnel. Make your way east until you reach the goblin mines (Picture) using the symbology provided in the book and the marker stones to walk the safe path.

Go up to Mistag (Picture) and do either a Goblin Dance or Goblin Bow, he will talk to you and ask you to tell the "ruler of the above" that they come in peace.

Speak to Sigmund and tell him that you made contact with the cave Goblins. After that, go to Lumbridge and once again talk to the Duke, he will tell you that he's missing some silverware and he thinks the goblins might be.

Go to the H.A.M Hideout, located north-west of Lumbridge (Picture), and picklock their trapdoor until it opens so you can enter. Search the first crate near the entrance, you will find the Duke's silverware.

Go talk to the Duke with the silverware in your inventory, and tell him you found it in the H.A.M Hideout. The Duke will fire Sigmund for trying to put the blame on the goblins and then give you a peace treaty which he asks you to give to them. Head back down to the cellars and go to the mine, if you talk to the Kazgar near the start of the tunnel he will lead you straight to Mistag.

Go talk to Mistag and give him the peace treaty, he will then send a goblin to talk to the Duke. There will be a cut scene where the goblins and the Duke will make peace (Picture - Picture), and outside Sigmund will swear his revenge before leaving (Picture). Once you finish the quest, give Mistag the Brooch for a free mining helmet (you can only do this once).