Plague City

Gathering the items

 * Dwellberries spawn in McGrubor's Wood west of Seers' Village. You can get in by squeezing through a loose railing on the north side. Additionally, you can buy dwellberries from Heckel Funch in the Gnome Stronghold on the second floor of the Grand Tree on the east side or even grow them yourself with level 36 Farming.
 * Rope can easily be bought in the general store in Ardougne for 24 coins, or from Ned in Draynor for 15.
 * Elena's picture can be found in Edmond's house. It's on a table.
 * A bucket and a water source can be found behind Edmond's house.
 * Milk can be obtained by using a bucket on a dairy cow. There are dairy cows on a farm near the north entrance to Ardougne, east of the sheep.
 * The fastest way to obtain the chocolate dust is to buy a chocolate bar from a baker in East Ardougne and grind it with a pestle and mortar. Chocolate bars can be bought from the bakery stalls in East Ardougne as well as Heckel Funch on the second floor of the Tree Gnome Stronghold.  You can also use a pestle and mortar or a knife on a chocolate bar, which you can buy in Yanille, Port Sarim, or from Heckel Funch.
 * Snape grass is most easily obtained on the small peninsula behind the Crafting Guild, alternately you can buy snape grass from Nightmare Zone points.

Starting the quest
Once you talk to Edmond, he'll tell you to talk to his wife about getting some sort of protection against the plague. His wife is just inside the house, and she'll tell you she can make a gas mask if you get her some dwellberries. Give her the berries, and she'll give you a mask. If you need a spare, there will be one in the cupboard. Also, make sure you get a picture of Elena while you're there.

Talk to Edmond again, and he'll tell you about his plan to dig under the wall and get into West Ardougne. First you'll need to soften the ground, though. Use your buckets of water on the mud patch behind his house, then use the spade you can find nearby to dig through into the sewers. You'll find Edmond inside as well. Walk south, and you'll find a pipe blocked by bars. Just use a rope on the pipe and talk to Edmond to pull the grate off. Put on your gas mask and climb inside to go into West Ardougne.



Finding Elena
Once inside West Ardougne, talk to Jethick. He's standing a few paces to the east. Show him Elena's picture. He'll tell you to go check the Rehnison house and give you a book that he borrowed from them. Head north and a little west (see picture) to find the house sitting right up against the edge of the wall. They'll let you in when you mention you have the book. Once inside, talk to Martha or Ted Rehnison and then go upstairs and talk to the daughter of the household who'll tell you more about Elena's whereabouts.

Head back out of the house and south of the town square to find the house the girl told you about. You'll recognise it because of a big black "X" on the door. Unfortunately, the Mourners won't let you in because it's been hit hard by the plague. Tell them that you're looking for a kidnapped girl, and they'll tell you you need permission from Bravek to enter the house.

Getting inside
Go back to the town square and go into the large building just north of the manhole. Ask the Clerk who is through the door, then tell him you're there for something very important and he'll let you inside to see Bravek. He can hardly talk to you, though, as he's badly hung over. He'll give you a tatty piece of paper with a recipe for a hangover cure. To make it, put the chocolate dust into the bucket of milk and add Snape Grass. Give the concoction to him, and tell him the mourners wont listen to you. After, he'll give you a warrant that grants the permission you need to go search for Elena in the Plague House.

Head back to the house and try to enter again. The Mourners will try to stop you, but when given the warrant from Bravek they'll be rather at a loss, giving you a chance to sneak inside. Elena is downstairs. In the only searchable barrel is the key to her jail door. Go downstairs and unlock the door and release the grateful girl.



Head back to the manhole to get back outside and talk to Edmond to end the quest.

Rewards

 * 1 Quest point
 * 2,425 Mining experience
 * A magic scroll, letting you use the Ardougne Teleport if your Magic is 51 or above. After you read it, you'll memorize the spell.