After completing the quest "The Doom in Wortham", when the cutscene ends, you find yourself outside Deckard Cain's apartment in New Tristram. Cain is dead, killed by Maghda. But he did manage to piece the sword together just before he died.

Talk to Leah standing outside her uncle's house. She is upset by her uncle's death, and by the fact she could not do anything to save him... if only she could control this newfound power of hers... But you tell her she should not blame herself, Maghda is the one who must pay for Cain's death. Maghda, and her master Belial. The journal speaks of "an angel falling from the heavens as the shadow rises from the Abyss." The Stranger is the key to all of this. You need to find the Stranger again, and bring him his sword.

Leah tells you that when her power erupted, she saw into Maghda's mind for an instant. She's fled to the Highlands. You can reach them through the caves above Wortham. You have to know she'll be waiting for you.

This starts the next main story quest:

Trailing the Coven
Enter the Caverns of Araneae above Wortham.

Before leaving, take care of stuff like crafting, buying and selling around town. You should buy some health potions if you are out. Also be sure you are wearing the best equipment you have, and that all of yours and your followers' skills are assigned.

When you are ready, use the waypoint, teleporting to the Wortham Chapel Cellar. Exit the chapel, and start heading north and northeast. Check the bodies of dead villagers on the way, for loot. You arrive at the Wortham Bluffs. Cross the bridge. You run across an NPC here, with an exclamation mark (Quest Giver). Speak to him.

Rodger the Alchemist: Hello Wanderer. I sell quality potions and dyes at a fair price. Have a look if you like! Oh and will you do me a favor? There's a lunatic down by the caves who wants a potion to make his blood sweet, if you can believe it. Would you mind bringing it down to him?

This starts a new event (side quest):

The Sacrificial Hermit
Deliver the Alchemist's concoction to the hermit by the Caverns of Araneae

Check out the Alchemist's wares. He has stuff like Minor Health Potions, All-Soap's Miraculous Dye Remover, Vanishing Dye, Spring Dye, Tanner's Dye, and Winter Dye. Once you are done trading with the merchant, continue towards the Araneae Caves. You will be going past a tower and down some spiral stone stairs. The Hermit is at the foot of those steps, near the entrance to the cavern. You give him the potion that the alchemist asked you to deliver. He says this is perfect, his mistress will now accept him. Her blood and his will soon sing as one. This completes the event, The Sacrificial Hermit. Next, go into Caverns of Araneae.