Start: Elena in East Ardougne. She lives across the road from Plague City start.
Requirements: Must have completed Plague City, 10 coins OR Priest Gown and Priest Robe, ability to kill lvl-22 NPC. Level 33 magic for Telekinetic grab recommended.
To begin, go to western East Ardougne and talk to Elena in the house just east of the house where the Plague City quest begins. She will tell the player about how she was able to collect some good samples of the plague, but unfortunately the Mourners took all of her equipment. She now needs someone to sneak back in to try to find it. She suggests that you talk to Jerico, since the tunnel you used to get in before has been sealed off.
Jerico lives in a house just south of the northern bank in Ardougne and just north of the church. He tells the player that he has arranged for Omart to help create a rope ladder to get over the wall. He will tell the player to go find Omart. Search the cupboard nearby to find some Bird feedand grab some Messenger pigeons from the backyard before you go. Omart is found west of Carnillean manor in East Ardougne, just south of the castle. He is located outside of the south-east corner of West Ardougne's walls. He will tell you to talk to Jerico. (You only need to do this if you didn't pick up a cage and feed the first time you spoke with him).
Now head to the Watch tower, north of the gate to travel between east and west Ardougne. Use the Bird feed on the Watch tower. Next, open the pigeon cage to release the pigeons. They'll immediately fly into the tower to eat the feed. This will distract the guards.
Go south to Omart and talk to him. He'll help you get over the wall.
Now head to Martha Rehnison's house first used in Plague City. It is located to the north of the sewer in the middle of West Ardougne. Pick up the Rotten apples on the east side of the house. Now use the rotten apple on the Cooking pot east of the rotten apple spawn. Walk around to the front of the building, and attempt to go inside. You won't be allowed in because several mourners are ill with food poisoning, and they are waiting for a doctor.
Head to Nurse Sarah, who is in the building south of the office building. Search the cupboard in her house to obtain a Doctors gown. Equip the Doctor's gown and go back to the house with the Cooking pot. The medical attire will allow you to enter freely.
Go upstairs and either talk to the Mourner (lvl-22) or attack him while still wearing the Doctor's gown. Kill him and a bronze key will automatically be placed in your inventory. Use the key on the gate to get inside the room. Search the crates to find Elena's distillator. Exit the Mourner Headquarters. Head back to where Omart helped you climb the wall at the south-east corner of West Ardougne and speak to Kilron. He will help the player get back over into East Ardougne. Go to Elena and give her the distillator.
Elena will extract a sample of the plague, but the results of her test are strange. In order to get further results, she needs some help from her mentor, Guidor. Elena will give the player a plague sample along with three reagent vials: liquid honey, sulphuric broline, and ethenea. Avoid teleporting or taking any damage while you have these reagents in your inventory, you should bank them first. If the items break, they can be replaced by talking to Elena again.
Take the sample and vials to the Chemist in the western-most building in Rimmington and talk to him. Select the second option that says "It's OK I'm Elena's friend." then the second option "Who knows... I just need some touch paper for a guy called Guidor". Do not choose the dialogue options that mention the plague sample, otherwise he will take it from you and you will have to get another. Once the conversation is finished, you will receive some touch paper.
(Note: If you can cast Telekinetic grab and want to save some time, grab 3 casts and skip to the next paragraph.) The Chemist will suggest giving a vial to each of his three helpers: Chancy, DeVinci, and Hops. They are located right outside the Chemist's house. They are unreliable, so you must choose carefully who to give each vial to. Give Chancy the liquid honey. It is worthless, so he can't sell it on the black market. Give DeVinci the ethenea. It is colourless, so he can't paint with it. Give Hops the sulphuric broline. It is poisonous and has a foul smell, so he won't drink it. After giving the vials to them, head to Varrock. Bank the plague sample if you are going to teleport there.
Once you are in Varrock, acquire a priest robe and priest gown. Both of these can be bought from Thessalia's Fine Clothes located on the west side of Varrock square for 10 coins. Keep them with you until the end of the quest. With the plague sample and touch paper in your inventory, go to the south-east part of Varrock where there is a guard standing in front of a gate near a tea stall. Attempt to open the gate and he will search you, but he will ignore the plague sample and will allow you to pass. Now, head to the Dancing Donkey Inn and talk to the Chemist's assistants to get the vials back. Your inventory must have space for the three vials. Having a full inventory will require you to obtain a new set from Elena. (Alternatively if you have level 33 Magic, you can drop the three vials by the fence near the tea stall, go through the gate and then cast Telekinetic Grab on the vials.)
Equip the priest robe and priest gown. Head to Guidor's house in the south-east corner of the gated area. Go inside and try to open the door to Guidor's room, Guidor's wife will stop you but she will think you are a priest and allow you in. Talk to Guidor and give him the vials, plague sample and touch paper. After analyzing the sample, he will come to a surprising conclusion: the plague sample is harmless. West Ardougne was an inside job!
Return to Elena in Ardougne and talk to her. She will tell the player to talk with King Lathas. He is located in Ardougne Castle, just south of Elena's house. Talk to the King. Quest complete!
3 Quest points
King lathas Amulet
Use of the Combat Training Camp north of Ardougne
Ability to travel freely through the Ardounge wall gate
Thieving Experience = (Level * 50 + 500) x Custom Rate