Complex sentence: In 1928 photographer Harvey Metcalfe attended a series of séances at Duncan's house and took flash photographs of Duncan and her alleged "materialization" spirits, including her spirit guide "Peggy".
Split into simpler sentences: In 1928 photographer Harvey Metcalfe attended a series of séances at Duncan's house. During a séance, he took flash photographs of Duncan and her alleged "materialization" spirits, including her spirit guide "Peggy".