Move along to Lowtown and enter Lirene's Fereldan Imports. Speak with Lirene to get word of Anders, a former Grey Warden. You can find Anders in Darktown in the northeast corner healing a young boy. Agree to aid him though be wary of what you say as it effects Friendship or Rivalry. If you've yet to explore the area of Darktown then head south to the Abandoned Mining Tunnels. Down the steps you will find deathroot and further down near Danzig you will find The Remains of Sister Plinth to start a quest.
Head to Hightown at night and meet Anders near the Chantry. Head down the hall and up the steps to the south to find a crate in the western room. Karl is in the northern part of the Chantry. Speaking with him triggers Templars to attack and in the end Karl will die. You can recruit Anders into the party after the scenes and you now have access to more Secondary and Companion Quests.