The action on Once Upon a Time flicks between the present-day "real world" and flash-backs to the characters' lives in the "Enchanted Forest". These flash-backs usually serve to illustrate how two characters know each other, or how their relationship evolved, or to show how much they have changed between "then" and "now". This is sometimes helped by the introduction of a guest character we haven't seen in the "real world", and this time it's Robin Hood!
In episode
2.19 "Lacey", we have Mr Gold trying to help amnesiac Belle remember their past life together (she used to be Belle, but crossed the town line and forgot her "real" self and now has only "curse" memories Regina implanted in her and thus thinks she's Lacey, a bar-fly). He's counting on her because she always brought out the best in him and he needs that support to continue growing as a person, to fight his wicked tendencies (and stop him from maybe killing his own grandson since a prophecy stated "the boy will be your undoing").
The flash-back shows us the beginning of Belle and Rumple's story (well, after she surrenders herself to the "beast" that is) and starts with Belle sobbing in a dungeon. Rumplestiltskin shows up to complain about the noise:
"Rumple: When you so eagerly agreed to come and work for me, I assumed you wouldn't miss your family quite so much.
Belle: I made my sacrifice for them, of course I miss them you beast!
Rumple: Yes, yes, but the crying must stop! Night after night. It's making it very difficult for me to spin! You know I do my best thinking then!"
The sound of broken glass takes us to an elegant room in the castle (possibly a study), where a hooded figure carrying a bow and a quiver of arrows is about to make away with a wand. He shoots at Rumple with "
an arrow shot from this bow always finds its target" and hits him. Unfortunately Rumple is "the Dark One" and cannot be killed! He simply pulls the arrow from his chest and we get treated to the #1 rule in Once Upon a Time:
"But don't you know? All magic comes with a price! And in your case, that's me."