Talk to Trufitus Shakaya at the house which is northeast from the Tai Bwo Wannai Village. When you ask him about the abscence of people in the village, he tells you that he is equally baffled. He, however, needs to talk to the gods regarding the matter and needs a potion to perform the ritual.
As he is old and frail, he asks you to gather the ingredients required to create the commune potion. The herbs he need are, in this order:
Snake weed
Ardrigal
Sito foil
Volencia moss
Rogue's purse
You will not be able to collect any of the ingredients before Trufitus has told you what needs to be collected. Therefore, you must go back to him after obtaining each herb.
Go south-west of Tai Bwo Wannai Village until you see some green and yellow vines (marshy jungle vines) near the shore. Search it and you will get snake weed. This might take several minutes. Clean the herb.
The herb is found by the fire remains on the south side of the boundary of Tai Bwo Wannai Village. Search the scorched earth there until you find a herb. Clean it.
If you are under level 65, armour and food or protect-from-melee prayer is highly recommended for this part.
Trufitus will tell you to find Rogue's purse. (You CANNOT use rogue's purse from the Shades of Mort'ton quest, from the Grand Exchange, or as drops from the jogres in the cave or the tribesmen. It must be from the walls. The walls will not yield unless you are given the task to fetch it.)
The herb is in a dungeon. The dungeon's entrance is found to the north along the coast, near the harpie bug swarms, which you must pass by. Search the rocks there and enter the cave. Beware of the aggressive Jogres that inhabit the dungeon!
All caves in the dungeon contain the herb, but the southernmost one has 6 herbs on walls. Search a wall with green spots (fungus covered wall) to find the herb. This may take some time. Clean the herb.
To exit the dungeon, climb up the rocks where you entered it.
Return to Trufitus, give him the herb, and claim your reward!
Upon the completion of this quest, one's Adventurer's Log will read: "Using my extensive knowledge of Herblore, I managed to put together the potion that Trufitus required. Hubble, bubble, toil and trouble!" This is a reference to Act 4 of the famous Shakespeare play, The Tragedy of Macbeth'.
When you enter the cave to obtain the Rogue's Purse, you can see the Brimhaven Agility Arena to the west.
After completing the quest, if you talk to Juna, your character will say, "...And once I had gathered all the herbs, Trufitus Shakaya was able to commune with his gods."