Susan Seymour was the fiancée of Richard Harries.
Susan called off the marriage after an argument with Richard. He attempted to make up with her but was interrupted. He was killed when his machine overloaded and he was burnt.
Inspector Ian Stratford and Sergeant Baker arrived; Ian offered his condolences, she did not seem to understand what for. She began to display period when she would be without emotion, her face taking on a pale complexion.
John accompanied her to view Richards body; she was visibly upset at reference to his injuries. However before they entered she changed; looking upon the viewing solely in a scientific interest. They entered along with the Inspector and Baker to find the body gone.
Susan and John grew close and discussed the murder.
Later, Susan visited Stratford and offered the explanation that the body was a clue. Startford took this into account as a good theory.
Susan was deeply frightened by Harries' return. He pursued the residents as they fled from him. They barricaded themselves upstairs. Friedlander deduced that Catherine was subconciosly controlling Harries. Catherine thought hard and stopped him. Friedlander, John, Ian and Baker then left to collect something to tie him up.
Catherine left, controlling Harries with her. She revealed that she used him to kill the others, hoping to clear his name and protect his honour. She sent Harries upstairs to attack. Susan and Kreiner abseiled out the window. Cuthbert Simpson was seemingly killed. Susan fell a long way but Hopkinson broke her fall; she sprained her ankle.
Susan and Kreiner climbed down the chimney, joining Ian and Baker in the drawing room. Freidlander and John also arrived followed by Harries who broke in. Catherine also broke in, she commanded Harries to kill Susan. He hesitated but eventually complied, strangling her. He was pulled away and she fell unconcious.
She awoke and was threatened by Catherine, jealous over Richards love for her. Susan told her that his love for her was greater. Harries' dismembered arm prevented Catherine killing Susan, showing her that he loved her more. Friedlander took Compassion out of her but she retained memory of the events.
Susan told Stratford that she still loved Richard despite everything he did. She told him he was different, not evil. After learning of Gordon Seavers' death, she immediately thought for his widow.