The haunted pajamas

the long version

"After spending three years in England, the Harvard educated narrator returns to America with a pair of pyjamas said to be over 4,000 years old. These can transform the wearer into a phantom-like figure and the young man uses them in a number of seductive exploits with very unexpected results."- - Description by Peter Haining, in "A Century of Ghost Novels 1900 - 2000" (Appendix to his book, The Mammoth Book of Modern Ghost Stories)