ARIEL TRAVELS TO STORYBROOKE TO CONTACT BELLE AND FIND A HIDDEN ARTIFACT THAT CAN HELP TAKE DOWN PAN, AND EMMA, NEAL AND HOOK ATTEMPT TO LOCATE DARK HOLLOW - WHERE PETER PAN'S SHADOW DWELLS - IN ORDER TO CAPTURE IT, ON ABC'S "ONCE UPON A TIME"

JoAnna Garcia Swisher Guest Stars as Ariel

"Dark Hollow" - Mr. Gold and Regina send Ariel back to Storybrooke with an item that will allow Belle to locate a hidden artifact that could help take down Pan. But unbeknownst to them, two men have broken into the town with the intent to stop them - at all costs. Meanwhile, Emma, Neal and Hook attempt to find Dark Hollow, where Peter Pan's shadow dwells, in order to capture it, and Mary Margaret is upset with David for keeping his poisoning a secret from her.