 After the breakdown by Roberts cut the revival short, he stayed with the Penn-Lewises for a couple of years, but never fully recovered.Ultimately, Penn-Lewis declared some of the phenomena of the Welsh Revival to be the work of Satan, declaring her still controversial position in her book on spiritual warfare called "War on the Saints", which describes the work of demons on Christians, the theme for which Penn-Lewis is most known.Penn-Lewis was influenced by the Dutch Reformed, South African writer Andrew Murray, among others, and her books contain quotes from him and references to his works.