During World War II, in November 1941, Duncan held a séance in Portsmouth at which she claimed the spirit materialization of a sailor told her HMS "Barham" had been sunk. Because the sinking of HMS "Barham" was revealed, in strict confidence, only to the relatives of casualties, and not announced to the public until late January 1942, the Navy started to take an interest in her activities. Two lieutenants were among her audience at a séance on 14 January 1944. One of these was a Lieutenant Worth who was not impressed as a white cloth figure had appeared behind the curtains claiming to be his aunt but he had no deceased aunt. In the same sitting another figure appeared claiming to be his sister but Worth replied his sister was alive and well. Worth was disgusted by the séance and reported it to the police. This was followed up on 19 January, when undercover policemen arrested her at another séance as a white-shrouded manifestation appeared. This proved to be Duncan herself, in a white cloth which she attempted to conceal when discovered, and she was arrested.