This episode has certainly closed the trap around Rumple, all of Belle’s actions this episode relate directly to Rumple’s lies and gave him reason why he couldn’t tell the truth. Every time Rumple was caught in the lie, his reaction was to panic and lie his way out of it thus digging himself deeper.
The Dagger- Belle attempted to use the dagger on Rumple. Because it was a fake, at least Rumple could do his best to keep Belle safe even if he had to play along with being controlled. For example, Going inside the cave and getting Belle and taking them back to the shop before the SQ came. He couldn’t have done that if Belle had the real dagger as he would’ve been bound to stay outside and he would’ve had to let go when Belle was telling him to in the cave. Thus he can’t tell Belle about the dagger because keeping her safe requires him to be in control of himself at all times.
The Hat- Belle knows what the hat does, she knows it’s not a good thing. Besides the fact that Rumple panicked and denied all knowledge of the hat, Belle’s attitude towards the hat suggests that if she found out Rumple had the hat all along and had used it, she won’t be very happy with him thus telling her about the hat is no longer an option for Rumple.
The lie- Belle is beating herself up over telling a small lie because she “knows Rumple would never keep a secret from her”. That line right there is the reason why Rumple can’t tell her he lied.
It’s the classic two people have something to say to each other, one happy, one not happy and because the happy one goes first, it prevents the unhappy one from saying their piece or vice versa if that makes sense. It is commonly used in tv when one character has “news”. For example, if a guy want to break up with a girl and the girl wants to tell him she’s pregnant. If the girl goes first, it prevents the guy from breaking up with her as he can’t just leave her in that situation. If the guy goes first, it prevents the girl from telling him she’s pregnant because she doesn’t want to tie him down.
Belle’s “I know you would never keep (a secret) from me” is that line.
Also Rumple doesn’t want to lose Belle. After Bae’s death, Belle is the only person left that Rumple truly cares about (maybe Henry too but that is more by proxy of Neal than Henry in his own right). Rumple’s lies are because he doesn’t want to lose Belle but ironically it is the lies that are going to cause him to lose Belle.
All magic comes with a price!
Keeper of Felix