The quest itself will initiate when you progress along the good path with the druid grove quest. Protagonist should be a single classed druid or shaman. Whatever hints you might have acquired beforehand will remain relevant. If I misunderstood your question and you have already started the quest, but stuck looking for clues, let me know.

1) discovering Annah in temple ruins: there will be a letter (I think it is in the container in her lair)
2) talking to dying Merella
3) discovering Grancor the werewolf in windspear dungeon (the dudes that masquerade as knights in distress)

if you're still stuck by the time the story plotline with Aran is done in CH3, a druid messenger will appear in the docks and give more specific clues to locate the rest of the stuff. Make sure you discover all clues and proceed through the storyline before sailing away to CH4.