Simon Peters was a man driven mad by exposure to the Cardiff Space-Time Rift and the subsequent disappearance of his wife. He later set up a religious cult dedicated to the rift, which he called The Glory.
In 2006 while walking home from a night out with his wife Elwyn, they were both taken by the Cardiff Space-Time Rift. Jack Harkness and Suzie Costello managed to rescue Simon, but Elwyn was lost in the rift. Suzie neglected to give Simon Retcon as an experiment, leaving him to cope with the loss of his wife to supernatural phenomena. He believed that the rift was an entity called the Glory and that he had been baptised by it, having gained the ability to control the opening of the rift to some extent due to his exposure to its energies.
Eighteen months later he rescued Elwyn from the rift, however she was gravely injured and passed away shortly after. By this point he had lost his grip on reality so severely that he didn’t notice that she had died. Simon carried on domestic life with Elwyn, as though she had never died. Months later, Elwyn's corpse was discovered by Jack Harkness and Gwen Cooper, who took it away from him.
Simon soon began preaching on the streets of Cardiff, telling people about the Glory. Over time he developed a following and he started to feed his followers to the rift, which he believed was a higher power destined to bring them enlightenment.
Three years after his exposure to the rift he fed Jack Harkness and Ianto Jones to it, and later Gwen Cooper witnessed him erasing a football stadium full of people. Subsequently Gwen lured him to Flat Holm, where she killed him and then took a Retcon pill to forget, as revenge for all the people he had erased from the timeline. (PROSE: We All Go Through)