Mystery, a 212-ton fishing trawler built at Tottenville, New York, in 1886, was chartered by the Navy in July 1918, taken over the next month and placed in commission early in September 1918 as USS Mystery (SP-2744). For the next four months, she supported minesweeping operations in the entrances to New York Harbor. With her services no longer needed following the end of World War I, she was returned to her owner in January 1919.