Biohazard

Talk to Elena in East Ardougne, directly west of the shortcut log. The mourners have confiscated her distillator, which she needs to test plague samples. She wants you to retrieve it, but the tunnel the player used to enter West Ardougne last time has been filled in. She suggests you talk to her father's friend Jerico, who has a method of communication with West Ardougne.

Jerico can be found in a house just south of the northern bank, and just north of the chapel. Talk to him, and he will tell you that he has used messenger pigeons to communicate with two friends who are going to help you with a rope ladder to cross the wall.

Open and search the cupboard on the north wall to find some bird feed, then go behind the house to grab a pigeon cage.

Ensure you have your gas mask, then speak to Omart, who can be found by the wall just north of the Battlefield Spirit tree, near Ceril Carnillean's house. He will ask you to create a distraction to occupy the watchtower guards before his assistant Kilron can help you over the wall.

Head to the small watchtower along the wall, directly north of Omart. Stand in the corner where the two spiked fences meet, put the bird feed on either fence, then click the cage in your inventory to create the distraction.

Go back and talk to Omart, who will call out to Kilron to throw over the rope ladder. With the gas mask equipped, climb over the ladder into West Ardougne.

Head to the Mourners' headquarters located in the north-eastern corner of the city. If you tried to enter you would not be allowed in; instead, head to the western side and squeeze through a gap in the fence into the backyard. Pick up the rotten apple laying on the ground just to the west of the fence hole, and right click to use it on the stew that is brewing in the cauldron for the mourners. If you tried to enter the headquarters again, they would complain that several mourners have been taken ill with food poisoning, and are in need of a nurse.

Head to nurse Sarah's house - the large building south-west of the West Ardougne church. Search the cupboard in the northern part of her house to obtain a medical gown. Equip the gown, and go back to the headquarters. The professional attire will easily fool the mourners into letting you into their base. For all subsequent visits to the headquarters during the quest, the gown must be worn at all times.

Go upstairs and kill a mourner. A key will automatically be placed in the player's inventory. Use the key on the gate to get inside the caged room. Search the crate third from the left on the northern wall to find Elena's distillator.

Note: Rings of recoil work against the mourner, after talking to him he will attack you and the key will still drop.

Go back to Elena by climbing down the manhole in the middle of the city and climbing the mud pile. Alternatively, Kilron at the south-eastern corner of West Ardougne will help the player get back over into East Ardougne.

Speak to Elena and the player will give her the distillator. After running the tests, she will be confused to find that the touch paper hasn't changed colour at all. She will give you a plague sample, liquid honey, ethenea, and sulphuric broline, and ask you to visit her old mentor Guidor in Varrock for guidance. First, you will need to visit the Chemist in Rimmington to obtain more touch paper and to find a way to smuggle the three vials into Varrock.

Make your way to the Chemist in western Rimmington, who will give you the touch paper; you need to have the plague sample in your inventory to talk to him about the quest.

Note: You may fast travel to Rimmington; the vials used to break when doing so, but this is no longer the case. For a list of transportation options to Rimmington see here.

The chemist will advise you to use his errand boys to deliver the goods, but warns you that they have a habit of stealing, and that you must give them each something they have no reason to steal.

Chancy the gambler, Da Vinci the artist, and Hops the drinker are located right outside the chemist's house crowding around a fire. Talk to each of them to give them their respective vials. If you give the wrong vial to someone, give the remaining vials to the others, speak to them all in Varrock, then return to Elena to get new vials before repeating this step.

Head to the fenced-in enclosure in south-eastern Varrock. The guard will search you when you try and pass through the gate, but will not find the plague sample; he will however confiscate the vials if you forgot to give them to the errand boys, and you will need to repeat the step.

The errand boys can be found in the Dancing Donkey Inn inside this area. With the plague sample in your inventory and three free inventory slots, talk to Hops, Da Vinci, and Chancy to get the vials back. If your inventory is full when you talk to them, you will need to obtain a new set from the chemist.

Warning: Now that you have the vials, do not leave the fenced area, or they will be confiscated on return. If you forgot your plague sample or touch paper, you can drop the vials at the gate, quickly retrieve your items from the Varrock east bank and then pick up the vials again.

Guidor is ill, and his wife Julie will not let anyone visit him, though she wishes for him to see a priest. If you didn't bring a priest gown, you can obtain one for free by talking to Asyff in the Fancy Clothes Store in this area. Equip your priest gown and then talk to Guidor in his house in the south-eastern corner of the gated area. Give him the vials and sample, and tell him that Elena has sent a sample that needs to be processed. After analysing it, he will come to the conclusion that there is no plague - someone has been lying about it.

Return to Ardougne, and talk to Elena. When you tell her that Guidor found nothing in his results, she suggests that the plague must be a hoax and that you should speak to the person on top of this - King Lathas of East Ardougne. King Lathas is located just south of Elena's house, in his throne-room on the 1^st floor (UK) of the East Ardougne Castle.

When told that the plague is in fact a hoax, the King replies that he did it for the best of his people, and that it protects them from a "far greater danger". He then tells the player about the journey of King Tyras - the king of West Ardougne and King Lathas's brother - towards the west and that he has been corrupted by the Dark Lord after drinking from the Chalice of Eternity. Hence, the wall has been erected between the cities to protect East Ardougne and in turn, all of Gielinor.

Congratulations, quest complete!