Legend of the Mortal Remains of St. John the Baptist

This is the outer face of the surviving wing, the side the congregation saw when the altar was closed, and it follows the fate of John the Baptist's body, the patron saint of the knights who ordered it. In the distance, after his execution under Herod, his head and body are buried separately. In the foreground, on the orders of the emperor Julian the Apostate in the year 362, the tomb is opened and the bones are burned. In the middle, the remains that were rescued from the fire are found again in the 13th century.

Geertgen set that last scene in his own day. The men standing in a row in their black habits are members of the Haarlem house of the Knights of Saint John, portraits of real people from the order that paid for the altar. The Kunsthistorisches Museum describes them as the earliest group portrait in the history of art.