Robert Carlyle
Robert Carlyle portrays Rumpelstiltskin and Mr. Gold in the ABC series "Once Upon a Time." Reuters

Rumpelstiltskin is coming into his own on the ABC series Once Upon a Time.

In Sunday night's episode, the trickster -- in a story arc that deviated slightly from the conventional fairy tale -- duped a desperate Cinderella into promising him her firstborn child in exchange for helping her get to the ball and meet the prince, thereby letting her leave the home of her wicked stepmother and stepsisters.

Cinderella signs his agreement without even reading it, which proves to be a huge mistake. Rumpelstiltskin, played by Scottish actor Robert Carlyle, later shows up to remind her of the promise she unintentionally made while she is still pregnant.

In the present-day setting in Storybrooke, Maine -- the town in which the fairy tale characters are unknowingly stuck in time - Rumpelstiltskin comes in the form of the wealthy Mr. Gold. His present-day name is a play on the original fairy tale, in which he spins straw into gold.

He is out to get the unborn child of Ashley Boyd, who is really Cinderella and portrayed by actress Jessy Schram. In the present day, Schram's character is a 19-year-old woman who is alone and desperate to raise her baby on her own -- and away from Mr. Gold.

But Emma Swan, ie the daughter of Snow White and Prince Charming who is portrayed by actress Jennifer Morrison, manages to save the day. She promises Mr. Gold an unnamed favor in exchange for his leaving Ashley and her kid alone. Ashley has her happy ending with her daughter's dad (really her original prince), but there is a hint of future conflict for their helper, Emma.