A surprise guest at Ben's mothers fundraiser offers to stop the overfishing which is jeopardising the mermaids' survival.
Chris escapes the facility as the military enter a state of high alert, but he's not the only one to make it out.
As the town of Bristol Cove comes to terms with a recent loss following an incident on the ocean, each of its citizens cope in different ways and it also provides a new education in human emotions for Ryn.
Those searching for Emma receive help from unexpected allies; Emma struggles to resist her dark urges as she tries to find Merlin before her transformation is complete.
Regina steps up in an unexpected way to protect Emma; a celebration at Camelot turns deadly; Hook tries to bring Emma back to the light.
