Then you go outside. You'll see the burglar dropped something. Pick this up, and you will see it is a runestone using engravings in a different language. Return to Sarah and provide her the rock. She will say that the Dark Wizards utilize these runestones as plans. Proceed to the Dark Wizards tower. When you arrive there'll be a cutscene with the Dark Wizards speaking with all the Dairy Cow at the corner of this area. The Darr Wizards say they're going to kill the king by giving him poisoned milk.
They say they are going to send him a letter encouraging him with their tower and providing them the poisoned milk instead of the normal milk. You will see them placing the milk on the table and the wizards heading out to give the king the correspondence. Walk within the tower and then empty the poisoned milk and replace it with regular milk. You'll see the toxin in the middle with just enough doses to fill the wizards poisoned milk. Simply take the cows and give it back to Sarah. Then after that you'll see a cutscene in which they wizards are meeting the king. The wizards will all die from poison, then the King will operate out the door straight back to Falador.
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