Little Boy Lost / Caught in the Thorns

I had this story idea back when I was running my Hunter game, and I've been prompted to think of it again following recent events in my personal life.
My idea for the Hunter game was to create a sympathetic antagonist that maybe they didn't want to stop, but probably should.
I settled on a Changeling freshly escaped from captivity and returned home from her time in the hedge, changed and confused.
The Changeling was taken when 10 years old, and has matured some 8 years whilst in Arcadia. Unfortunately time in our world has not moved as swiftly, and she has been gone only a year.
Of course, she hasn't been missing. A Fetch took her place and has been living her life for the past year.
When the Changeling turns up at her family home, she finds an 11 year old girl made of twigs and leaves who looks like she did and answers to her name.
Her family turn her away and call the Police.
She escapes, and with nowhere else to go, follows her family.
The Fetch fears discovery greatly, and begins manifesting powers to evade detection and to expose the Changeling, but not before a family member is convinced of the truth.
Acting together, this 'converted' family member and the Changeling kidnap the Fetch, their intent to find out what it is and what is happening.
At this point, the Hunters enter. They are alerted by the kidnapping, and the reports of the strange girl and her insane stories.
As they track and find the Changeling, she uses her obviously supernatural Contracts and abilities to escape.
She returns to where she has the Fetch imprisoned, and as the Hunters confront her again, the Fetch is killed and explodes in a shower of leaves, string and rags.
The Changeling collapses as if wounded, and the perceptive amongst the Hunters will notice a ragged shadow escape from the Fetch's corpse and flee to the dark corners of the room.
This story arc should take about two sessions to play out, and hopefully should surprise the Shit out of the players.