Plot: Puzzles involving the Chisholm Trail, Houdini posters and a flag that may have draped the coffin of President William McKinley, assassinated in 1901. Included: determining how far south the Chisholm Trail extended; checking the authenticity of Harry Houdini posters for a Chicago magic show; learning if a flag handed down to the great-grandson of McKinley's bodyguard actually adorned the 25th president's casket