In January 2015, Marvel announced that the sixth episode would be titled "A Sin to Err", to be written by Lyndsey Allen, with Stephen Williams directing [REF].
In January 2015, Marvel revealed that main cast members Hayley Atwell, James D'Arcy, Chad Michael Murray, Enver Gjokaj, and Shea Whigham would star as Peggy Carter, Edwin Jarvis, Jack Thompson, Daniel Sousa, and Roger Dooley, respectively [REF].