Crafty, crafty Riddle. Man, I would have fallen for his lies, just as Helena did! How does he do it?
You captured Tom perfectly! How I sometimes wish I was a character in this story that knew Tom...

Brilliant story line, well written.
Just a few mistakes I spotted:
On the first line, I think that 'change' should be 'changed'.
Later on, you say vaunting ambition, but shouldn't that be vaulting ambition? A short quote from Shakespeare's Macbeth, I believe.
Apart from those errors which were probably just typos, a really good piece.