Rebecca (played by Emily Head) took the jewel temporarily with the intention of getting it engraved as a surprise for Chrissie (Louise Marwood).
The siblings had quarrelled a lot lately and Rebecca thought the gesture might quell Chrissie's anger.
However, in scenes set to air tonight, the younger White sister panics as she realises the ring is missing.
Luckily her good friend Robert (Ryan Hawley) and his fiancé Aaron (Danny Miller) are on hand to help.
Emmerdale: Rebecca White panics as she realises she has lost Chrissie's ring
Emmerdale: Rebecca took the ring away to be engraved
She will never forgive me
Frantically searching outside of Home Farm, Rebecca says: "You don't understand I cannot have lost this ring. It was my mothers.
"Dad literally just gave it to Chrissie, she already thinks I am betraying her. She'll think I've done it on purpose the day before Lucky gets sentenced.
"If I've lost it she will never forgive me."
Emmerdale: Rebecca knows her family will be angry about what has happened
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Emmerdale: Chrissie lies lifeless after Rebecca pushes her over the bannister
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But what Rebecca does not know is that a conniving Chrissie has deliberately taken the ring to set her up.
When Rebecca realises her older sister's deception the two have a vicious argument at the top of the stairs, which ends with Chrissie lying lifeless on the floor.
Will Chrissie survive the assault? And will Rebecca own up to what she has done?
Emmerdale continues tonight at 7pm on ITV.