The legend has it that Tam Lin collected either a possession, or the virginity of any maidens who passed through Carterhaugh. A young maiden called Janet came to Carterhaugh and plucked two roses, whereupon Tam appeared and asked why she was in Carterhaugh without his command and had taken what was his. She stated that she owned Carterhaugh, as her father had given it to her. She then went home, and discovered she was pregnant, and announced that her lover was an elf and that she loved him. She returned to Carterhaugh, and discovered Tam was a mortal man, who, after falling from his horse, was rescued and captured by the Queen of the Fairies. Every seven years the fairies paid a tithe to Hell of one of their people, and Tam was fated to become that tithe on that night (Hallowe'en). He was to ride as part of a company of knights, and Janet would recognise him by the white horse upon which he was riding. He warned her that, when she caught him, the fairies would attempt to make her drop him by turning him into all manner of beasts, but that he would do her no harm and when he was finally turned into a burning coal she was to throw him into a well whereupon he would reappear as a naked man, and she should hide him. Janet did as she was asked, of course, and won her knight. The Queen of the Fairies was not best pleased, but acknowledged her claim.
There are many versions of the Tam Lin story, but that summary of Child 39A (from The English and Scottish Popular Ballads by Francis James Child) is considered to be the earliest.