Back in the Eastern Plaguelands, you and your companions in Fiona's Caravan finally reach Light's Hope Chapel, the base of operations for the Argent Crusade. This organization was essential in the defeat of Arthas during the Wrath of the Lich King expansion. A statue of the greatest hero (besides yourself) during the fight against the Lich King, Tirion Fordring, has been erected in front of the chapel.
Fordring is a paladin, former ruler of the Eastern Plaguelands town of Hearthglen, and former member of the Order of the Silver Hand, a group of paladins that was dissolved by Arthas shortly before he went mad and became the Lich King. Fordring was also exiled for allying himself with an orc who had previously saved his life, and attacking Alliance troops who were going to execute the orc. Prior to Wrath of the Lich King, you helped him discover that in his absence, his son had joined the Scarlet Crusade, and during your attempts to free him, the younger Fordring is killed. His son's death is what inspires Fordring to come out of hiding and lead the attack on Arthas. After his successful campaign, he is renamed ruler of Hearthglen, and can be find in its main keep.
You, Gidwin and Tarenar all take a series of tests inside the chapel, and its crypt, and are named members of the Argent Crusade.
Gidwin, frustrated by what he feels are the menial tasks given to your group, and anxious to fight the Scourge, runs off on his own, and is captured by the Scourge. You and Tarenar find out that he has been taken to a slaughterhouse in the Plaguewood section of the zone, and, joined by the other members of Fiona's Caravan, you kill the Scourge Baroness who has taken him captive, and set him free.
The other narrative in the Eastern Plaguelands deals with the mopping up of the scattered remains of the Scarlet Crusade. They occupy a stronghold in the southeastern part of the zone named Tyr's Hand, but upon closer investigation you discover that all of the Scarlet Crusade forces are now undead, meaning that they have become exactly what they most hated.
To discover what has happened to the Scarlet Crusade, and to see the consequences of Arthas' actions when he made his fatal choice, we need to enter the dungeon instance of Stratholme, the city of the damned.