"City of Mercy" is the eleventh episode of the thirteenth season of ER. It first aired on NBC on December 7, 2006. It was written by David Zabel & Lisa Zwerling and directed by Stephen Cragg. It's a Christmas episode that has Luka Kovač and Abby Lockhart deal with the Curtis Ames situation as Luka makes a heartfelt confession to her. It also has Archie Morris learns the true meaning of Christmas as he plays Santa for a special little girl.