The ballad of 'Tam Lin' was first written down in 1549. It's one of the oldest, oddest and most enduring of all folk songs, with literally hundreds of different versions and variations on the central theme of enchantment, true love and transformation.
In 1970, Roddy McDowall directed a film version, which retained the essential strangeness of the subject matter but added some groovy elements, some clever updates and music from the brilliant Pentangle. The music I've added to the clip is a Pentangle outtake (not from the soundtrack), and I've messed about with it.
You may well wonder what's going on. The following extract may or may not help.
"They'll turn me in your arms, lady,
Into an esk and adder,
But hold me fast, and fear me not,
I am your bairn's father.
They'll turn me to a bear sae grim,
And then a lion bold,
But hold me fast, and fear me not,
And ye shall love your child.
Again they'll turn me in your arms
To a red het gand of airn,
But hold me fast, and fear me not,
I'll do you nae harm.
And last they'll turn me in your arms
Into the burning gleed,
Then throw me into well water,
O throw me in with speed.
And then I'll be your ain true-love,
I'll turn a naked knight,
Then cover me wi your green mantle,
And hide me out o sight."